He's being sarcastic because the standing theme on the internet for most of the last decade is that Musk is an idiot who only got where he is because his parents are rich or he stole from other smarter/harder working people. SpaceX tends to put a hole in this idea since he founded and funded it himself, and they've made more progress in space travel in the last two decades than all existing government organizations and contractors have since the 70s.

The people that dislike Musk (or are afraid of the mob that will go after them if they say something positive about him) can’t deny the amazing things he is accomplishing and so when anything good happens, they are quick to farm karma with thanking and congratulating everyone who isn’t Musk. It is intentional.