Often it's because they have enablers who actually let them screw them over while still covering for them.

So they keep thinking everyone else is a sucker. Until they're stuck in a room with only defectors around and no enablers.

On the other hand, the is this story about a professional poker player teaching a poker class.

When she asked her students can you deduce when a player bids high on a hand. Most of the students answered that the player must have a good hand.

The pro player was baffled by this answer and asked them what they would do if the had a good hand. The same students answered to bid low or check so the other players won't fold.

Than she asked why they expected other players to do the opposite of what they would do.