There is a very very simple explanation, which is that everything he says is true. There is a secret program, they did reverse engineer, they did withhold it from congress, and people did tell him that there is alien stuff.
Why make up silly make believe?
The guy isn't claiming 'oh i saw aliens'. He could simply be telling the absolute truth.
Why so many people told him there were aliens, I dunno, but who cares. Those people aren't the ones whistleblowing and so it doesn't really matter, does it?
I for one believe the guy, 100%
My only complaint is that perhaps he should probably be a bit more circumspect about what actually exists.