I'm really not sure how anyone here can, or not, be so sure about the real situation. There are two sides to every story. And so often no one is pointing out any issues with someone, until they leave, and suddenly they were not competent, hard working, etc. Seen it happen 1,000 times in the corporate world.
Was that the case? I don't know, and unless someone has access to the entire roster and staff, neither does anyone here.
All I can do is guess and, for me, it's likely he was not a good fit anymore. But if anyone is sure of that, and I am not amongst them, cite your sources. And there better be more than 1.