It's abundantly clear that there are plenty of loons walking among us, and that fame, wealth, and authority absolutely do not exclude a person from being a loon.
I'm not saying David Grusch is a loon. I'm saying that, between "there is a government conspiracy to hide the fact that actual intelligent extraterrestrial beings are visiting Earth, and the government is collecting their technology and reverse engineering it" and "the guy who truly believes that is a loon," one of those statements is far more likely to be true than the other one. One of those statements would require a huge number of people to be completely silent about such a thing for decades, and the other would require one loon to believe it.