>>212212553 (OP)Because he realized that close people will hurt him eventually and the pain would last for years before he will manage it, and their existence doesn't make his life as happy and good to make up for such possibility.
He found he enjoys the solitude more, because it gives him the freedom from the pain caused by other people. The only person who can hurt him now is him himself, and he CAN manage that.
He is literally me.