Trust is something very fragile. You can have moments with people, that seem to connect both parties on a deeper level. That moment of shared experiences and other common interest can seem quite obvious. Then, at some unforeseen time, that fragile connection can be forever shattered and never mended.
What turns people on to betray? Perhaps in their social arena they can moved forward to a new level of authority & dominance..? Maybe hurting others is what makes them happy. By ruining the "trust" they have known intelligence that someone else is as miserable as they are. Maybe they feel elevated & superior over the person/ people they hurt..?
I wonder if they see their prey on the horizon or are these deceivers opportunistic, waiting until they have just enough information to tear the other person down? I would guess a mix of both. I would be lying if I said I never broke the trust bond. I've learned over time, it is wise to be open to the idea of trusting others. It would also be to our benefit if we were careful with bits of information that we share. If you can express ideas and perspectives in an articulate manner, chances are like minded individuals will stand with you, even if the idea is not popular.