Without going into the details of how and why any specific person came to have a specific belief, I have the following heuristic: when someone makes a claim, especially when the stakes are high, I ask "who does that benefit?" Now that doesn't mean that they're intentionally trying to benefit whomever that benefits. It doesn't mean that they're wrong.

So, Russia invaded and occupied Ukraine. Who does it benefit to be claiming "there should be peace?"

Obviously it benefits the invader.

It's easy to have peace, you just have to surrender.

Another heuristic that I have is to ask: "do this person's claims always benefit the same side?"