He got fed up by negativity or, more exactly and to quote one of his last PM to me, by "not very nice banter" and "stupid irrelevant remarks".
This is for a similar reason that Steveandpenny and a few others before him have found another hobby.
Please note that if these users were all reproaching the same tendency, they were not characterizing the whole community like this. Just a tiny minority but this was enough to spoil their enjoyment. To be honest, I can't blame them for their choice.