I'm not using the term "predator" lightly, either. It's polite to call him "a player." More likely he's a sociopath/psychopath. People think that word means serial killer, but that's a small number that do that. Most of them walk around us all the time. There are probably a few on these boards. It's hard to get your mind around it if you have a soul, but they really exist.
She might not know what made her so vulnerable, but HE did.