Agree with pp, it's darvo.
How about this op, if your mate said to you - my bf has done something awful (cheating/lying to me ect) and I asked him why he did it, how he could possibly do that to me? And in response, he blocked me, accused me of being needy or nuts and then, popped up again a month later as if nothing had happened. What would you say?
Something like 'well he is a fucking asshole. Block his number and never contact him again'. And that, would be the right answer.
He was messing with your head, punishing you by disappearing when you called him out in his bs. Trying to train you, to break you so that you would let him away with whatever horrible thing he had done.
You aren't crazy - because you had a normal reaction to someone doing something horrible.
But he would have called you crazy until you became it if you'd stayed. Until you broke. Until you just let him treat you like shit and said nothing. Abusers want you to doubt who you are, they want you do focused looking knwards that thry, can do whatever they like because you're no longer looking at them as if they are the problem. Because they've convinced you it's you.
After this abuse, you'd be wise to stay single for a while and spend time learning to love yourself. And reading up (throughout life) how to spot abusers like him in future so that they xannot get their claws in again.
Good on you for getting free of him though. Take some me-time and be kind to yourself.