No one will defend what you forced through
At the time, you pushed it through with momentum, and the other party even said, 'Understood, let's go with that.' But two weeks later, a name you've never heard comes up, internal discussions are underway on their side, and before you know it, you're back to square one. There is something about this that I don't want to just dismiss as 'it happens'.
This is a continuation of Everything is correct, but 'this isn't it' from last time. I am speaking from my experience as a PdM and business manager at an IT venture. I would be happy if you could read this as one perspective.
The table gets flipped with a time lag
This often happens in dealings with external parties. Projects pushed through by sheer force of will quietly revert to the beginning later on, as other people appear or internal reviews start for some reason.
And the points raised at such times are usually valid. Things like, 'What about the cost-effectiveness?' or 'How does this balance with other priorities?' Since it's business, these are questions you'd naturally expect, and in fact, it would be more concerning if they weren't asked. Since they are all valid points, there is no way to argue against them.

At this moment, the person in front of you who said 'let's go with that' isn't necessarily betraying you. It's just that they haven't invested their own weight into it, so they have no reason to defend it. Something decided by being pushed through is not a decision of the person who was pushed; when a logical argument comes along, they simply yield.
That said, it doesn't always end up as if it never happened; in fact, it might be more common for things to proceed as planned. Once it becomes a fait accompli, it's a hassle to crush it head-on, so everyone just goes along with it for now. Since it's not a strange story as a concept, it might even generate some numbers. But because both the proposer and the acceptor are moving forward without feeling entirely convinced, when a review timing comes around in six months or a year, or when the person in charge changes, it quietly fades out without anyone strongly stopping it. This is more troublesome than being opposed and crushed, and since it can look like a success in the short term, the person involved doesn't really know if it went well or not.
What is decided and what you have decided are quite different. So, what should you do to get the other party to invest their own weight?
What to hand over before it is decided
Pushing something through is an act of trying to move the other party's judgment itself. Being in a position to decide, or simply having a loud voice. It's fast, and the results are easy to see. However, it's not a trick that works on everyone, and I feel that more often than not, you aren't in a position where you can push things through anyway.
There is another way, which is not to change the judgment itself, but to change what the other party looks at when making the decision. If pushing through in a meeting is the former, distributing materials that organize the points of discussion before the meeting is the latter.

The latter requires no authority. The other party still thinks they decided it themselves, but the content of the decision has changed. Moreover, because they decided it themselves, they have invested their weight. Even if a logical argument comes later, that person will defend it themselves.
I decided to call this weak force. Its action is slow and it's hard to measure if it's working, but the good thing is that it doesn't require authority, and even if you reveal the trick, the relationship doesn't break.
There are many ways
'Handing over loose constraints,' which I wrote about last time, is also one of the weak forces, but there are many others. When I line them up, it's a bit interesting because it feels like I've given names to things I was already doing. They are things like this.
Mix it into casual conversation. If you propose it in a meeting, it becomes a matter of agreeing or disagreeing, so during the casual conversation before that, you subtly indicate the direction as one of the possibilities. Things mentioned in a place that isn't for deciding will slowly settle into the other person's mind.
Bring up stories from other companies with a slight twist. When you find something other companies are doing that you know your superiors wouldn't go for if presented as is, you abstract it once, shift the center of gravity slightly in the direction you want to take it, and then bring it back to the concrete. Like, 'I think that basically means this, but wouldn't this way of doing it be better for us?'
Set the framework first. At a stage where nothing is set yet, you set a frame that leads to a direction you are good at and comfortable with (a bit sneaky). I feel that what kind of story it started as initially has a significant effect later on.
Design who says it. Get the story through to someone close to the core who is trusted first. Even with the same content, how it is received changes depending on whose mouth it comes from.
Choose when to say it. If you want to proceed slowly, wait for a time when the other party has some breathing room. If you bring a long story to someone who is in a hurry, they won't have the space to accept the premises.
In none of these cases am I trying to make the other person decide. I am simply shifting the materials before the decision is made.
Is this manipulation?
I find myself wondering that even as I write it. Am I just rolling things along in my favor?

When I reveal the trick to them later, will they be convinced, or will they feel like they were tricked? That is likely the dividing line. I can say, 'I brought that case study because I thought it would be effective if you interpreted it this way.' In fact, saying that makes things go faster next time.
There are also things I cannot say. Like when I wait for a moment when the other person is swamped, skip the detailed explanation, and push them to the point of saying, 'Okay, let's go with that.' I have done this myself, but that is probably wrong. I cannot tell them later, 'You looked busy, so I had you decide while I could,' and since what I am doing is not much different from forcing a decision, when things settle down, they end up saying, 'Was that really what we talked about?'
And things where you cannot reveal the trick do not last. Even if it works once, they will be on guard next time, which ultimately increases your own costs. This is not about ethics; it is simply about sustainability.
When it does not work
Weak influence is by no means omnipotent; there are situations where no matter what you do, nothing will move.
The most common case is when the other person already has a concrete vision of 'how they want to do it.' Even if you try to work on the premises, if that part is set in stone, there is no way to touch it. Other cases include when the deadline is tomorrow, when it is a one-time interaction, or when the other person has no discretion to begin with. Time, the continuity of the relationship, and room for judgment—if any of these are missing, nothing will likely happen.
When dealing with someone whose vision is set, I give up for the moment and go along with their flow to get things moving. Then, I use the results that emerge along the way as new material. Since things that are already in motion are hard to ignore, this can sometimes be faster than debating with documents. Well, it is a detour, though.
What it means to be slow
I say this after writing all of this, but the tricky part about this approach is that it is hard to tell halfway through whether it is working or not.

There is a lag between setting the premise and the other person taking action, and the better it works, the more it looks like 'the other person decided it themselves,' so the credit is not visible. Sometimes, about half a year later, I see something I had suggested appearing in a completely different project. It is a feeling that is both happy and a bit lonely.
Perhaps this is the exact reverse of the forced decision-making I wrote about at the beginning. Strong influence works quickly, but it also stops working quickly. Weak influence takes a long time to start working, but when it does, it has become the other person's own, so it often remains even if the person in charge changes.
Therefore, there is an aspect where it cannot be used if you cannot wait. If you get impatient halfway through and switch to forcing the decision, you will ruin everything you have built up until then. Once they learn that 'in the end, you will just push it through,' they will stop taking you seriously next time.
Sometimes I feel like I cannot move anything without authority, but I suspect that is not the case at all; I just might not know the techniques I can use. I have summarized those techniques in Management that moves things with weak influence. For example, The story about when I felt the approach was wrong but couldn't say so and so on.
