He's been busy writing Urbit (and raising a family.)
One of the sad facts of the internet is, whether you are the one saying "[X person] is a racist" or "[X person] is not a bigot", to the casual observer all they see is (conversation) "[X person] blah blah racist bigot."
I can understand why this decision was made, even if I don't agree with it. The people calling out Yarvin would have made it uncomfortable for everyone. So, go ahead and get on with your conference then.