Maybe he lost interest because of all the bullshit Elon Musk promised that came to NOTHING, remember a few years back he promised there would be manned missions to Mars now... NOW!!! MANNED MISSIONS!!! They were supposed to be well along building a base on Mars that should have started 2 years ago!!
Reality may seem kind of dull compared to the fantasies Musk promised.
Personally I never believed Musk for a second, and I thought Neil Tyson was a blabbering idiot for parroting him. But many fell for it, and my wife thought I was "negative" for not believing and agreeing with them!
But things like the James Webb telescope are 100% cool.