We don't know why exactly he left. He just stated personal problems, and told people to unsubscribe to him. Though I think he just managed to get around $200 a month (cause he was talking about how he hit his $200 goal and bringing in a writer to help him write the story/dialogue), so it's not that much money for the amount of work he was putting into making the game.
He still logs into F95 every once in awhile, so he's at least alive. And who knows, maybe he'll dust off the ol' drawing board and start back up in the future. But it was a great run while it lasted.
But please, don't bother him asking to come back. He'll come back when and if he wants to come back.