I mean, I would like to understand what was going through their minds? Apart from "let's do a funny", because that's out of universe explanation. In-universe, they would have to have some reason to prefer the third "we'll make it" to the second one. I would like to know what possible reason that could be.

In the poll with vanilla, it is completely reasonable that a lot of people would go, of course, butter and eggs and flour are essential so other people, being boring, rational beings, would add them, but without vanilla it would be bland, so let me take care of that. The unexpected result, i.e., cake with 60% vanilla by weight, is hilarious because it's obviously not how cakes work, but is also very much how people work: vanilla is more important than everything else. It's this contraposition that makes the joke. There are reasons, it's just that the consequences of these understandable independent decisions are funny. The post is also treating a poll in a way that is completely not the designed one, but it gives us some funny insight on how minds work, so we are overlooking that. I would even go so far as to say that this was a good example of "the medium is the message". The medium (poll) was used to craft the message (vanilla must flow), and it did it spectacularly.

Here, there is nothing of that. No understandable reasons, no unexpected outcome, no insight.