Smart people are reluctant to express confidence because they are better able to understand all the ways they may be wrong. Unintelligent or uninformed people are more likely to be confident. Listeners get much more satisfaction listening to confident people
While true, veritasium is terrible and fakes science experiments for advertisements. You shouldn’t support him.
This is the first I’m hearing of this, usually it’s the opposite. Care to provide justification and evidence?

The one instance I’m referring to that caused me and my wife to stop watching was when he faked a science experiment for a wet wipes company, showing that wet wipes are flushable and used a faked experiment to show why.

You should not need proof for why this experiment was faked, but you can also just go find the video yourself and watch it. It’s so blatant that it doesn’t really need proof. And any wastewater engineer would tell you that wet wipes are not flushable as well.