I really feel like M. felt like he was entitled to your love. He felt like he showered you with love and affection, so you should have wanted to get together with him and marry him.

I just wrote a piece called "Bad Boys are Better Than Nice Guys" (which I'm not linking because I'm not trying to use this comment as an excuse to drive traffic), but it's literally exactly about this: men who go too fast, expect too much and cling too hard, are often misogynist (he's contacting you probably without telling his wife), and then blame you for not fixing their broken heart. I argue Bad Boys are better, because at least they have confidence and aren't hypocrites. I think ghosting him was not so terrible you owed him any time of day 20 years later. He may not have been safe to just break up with. I should know.