Why do girls happen to fall for Bad boys?

Then you have biased eyes. Some do, many don't.

"bad boys" seem to be confident (falsely so)
assertive (really, just impulsive)
worldly (false, just bold, braggart or liar)
charming (really, manipulative, narcissist)
exciting (really, risk takers)
and good looking (maybe - all the things above make one so)

Young girls think these characteristics are charming UNTIL they grow up and see it's all false bravado.

Some women are attracted to this kind of guy all their lives.

I can think of a few high school guys that all the girls were in love with. Years later, one is dead and the other has a long rap sheet with the law.