Woke up to a random hate text from ex. Thinking about breaking NC.

Late 20s male. Early 20s male breaks it off after 2 months and messy break up garbage. A month ago I send a offmychest email that was not the nicest but not even close to malicious. He texted me that night about it. We "talked" and have been in contact a little, I told him if he needs to ever reach out, I'm here like a friend. (Not usually my style but with some of the issues involved I felt it was important)

I wake the other day to a "I hate you for sending that email and wish the worst for you" he sent when drunk. It's been a month since I sent that email. And we had talked about it. We've never spoken that way to each other.

We texted a week ago but even though I miss him I decided to go NC until summer unless he "needed" me. I'm thinking of asking him though if he is ok and if he's really that miserable about our break up which he initiated. I've been the one that's miserable. What do? Keep NC? Why?

And why do people do this?