A lot of men are addicted to the validation of being desired, not the responsibility of maintaining a healthy relationship. The chase feeds their ego more than the actual connection.
Some people will swear that you are the problem. Yet, after you leave, their lives remain exactly the same: the same habits, the same issues, and the same chaos. That is when it hits you; it was never you. They just need someone to blame so they don't have to face themselves.