What is even more naive is thinking there are no other colleagues "that they haven't found a situation to screw you and the rest of the team yet, and that when such a situation happens, there's a chance they will act accordingly".

Just because you do not know whether someone cheated on their spouse does not mean they did or didn't or would or wouldn't. It means you don't know.

And just because someone did or was willing to do something in one context does not mean they would do so in another different context, but they would probably do so in a similar context.