The simplest explanation is usually true, and in this case, it's that he has decided he needs to move on from you/this.
Perhaps he's realised that he still holds those three months in high regard, or that he still has feelings for you, and that's not appropriate in a relationship. Perhaps his girlfriend is uncomfortable with the relationship between you, or has seen your conversations and thinks he has crossed a line in being so open with you. It could even just be that he's noticed that he uses you as a therapist, half the world away, and that's not very good for him.
I expect that when he had his accident and asked you to attend, he thought you were a true friend, and when you didn't go, that started the timer on the end of this. It's not really a real friendship. He confides in you because you're far away and he finds you easy to talk too, but you haven't seen each other in eight years, there's no regular chatting or anything else that indicates a proper friendship.
Whether he thinks blocking you is a way to get over you or he just doesn't want you to be an anchor to his past, you might never know. Maybe he'll unblock you at some point. I'd leave it be now regardless.