Why did he act this way?

He seems like a bitter guy, attacking you when he gets the opportunity. I think he needs to find some happiness in his life, but I am glad to hear that you have reached a better place after the break-up. Usually after break-ups, with hindsight we can see things how they truly were in the relationship. Taking a clear view we can see that not everything was rosy. Just chalk this up to a moment in your past that you have moved on from and continue to find new happiness in your life.