Space

Re: the specific argument about a coverup being impossible, there have been plenty of people over the years with claims like this. The idea that this guy is talking about what "a friend of a friend" said is also a very ungenerous and inaccurate claim, given Grush's established credentials.

Otherwise, I agree it's hard to believe, but I don't think this guy has actually "debunked" it as he claims in his hashtag. The options are that he's lying or crazy, and he doesn't seem crazy, and if he's lying he's going to jail. The most plausible explanation for it not being true is that it's part of some complex psy-op, but that also is a fairly outlandish theory (albeit not as difficult to accept on its face).