Nobody has claimed "it all just came from the usual suspects". Just that the usual suspects exert a strong influence on the rest of the believing community whom Grusch has been evidently mingling with both within and without the DoD.
How about looking at it this way:
The U.S. Department of Defense is the largest employer in the world, with over 1.34 million active-duty service members, including soldiers, marines, sailors, airmen, and guardians. DoD also maintains over 778,000 National Guard and reservists, and over 747,000 civilians bringing the total to over 2.87 million employees.
42 % of Americans believe in UFOs and 39 % in ghosts. One in ten Americans report that they have seen a UFO.
If the DoD represents a rough a cross-section of the American society (with the major exception of gender parity) -- and let's keep it conservative and assume only 30 % of DoD personnel believe in UFOs and 20 % in ghosts -- we'd still be left with 861,000 UFO believers and 574,000 ghost-believers.
(By the way, in comparison, 22 % of Brits believe in UFOs and 7 % believe having seen one.)
I'm pretty sure there are many, many informal circles of believers, as well as an ample amount of mutual camaraderie, amongst believing active-duty DoD members sharing amongst themselves all manner of rumours as to what they believe the DoD hides, and also their own alleged UFO sightings. Hence I deliberately used the term "gossip corners" and it wasn't really meant in disrespect. In other words, there's no shortage of DoD believers for Grusch to interview. True, hardcore, believers are no doubt a smaller percentage but I would suspect in an organization as huge as the DoD they'd still amount to a significant number of individuals.
We often see what we believe, while certain beliefs (such as UFOs) are culturally and thereby geographically specific. It's essentially the case of confirmation bias meeting folklore affecting human perception and hypothesis-formulation. UFOs are modern Western folklore which is especially pronounced in countries with a considerable percentage of sci-fi enthusiasts, and further reinforced by film, literature and media visibility (some of that visibility being deliberately promoted by the UFO lobby, including financial sponsorships). It's a powerful feedback loop.
If you'd ask the average American "have you ever encountered a djinn?" (the evil spirits in Islamic tradition), I'd wager you'd get a very different ratio of 'believers' as well as 'sightings'. With ghosts you'd likely get a fairly universal one, and so on and so forth.
Long story short: Anecdotes from lots and lots and lots of believers constitutes weak scientific evidence. But since that's about all that ufology has to offer, anecdotes by large numbers of people, anecdotes from people of impeccable service record and high ranking, coupled with blurry pictures and footage, remain the go-to evidence to bring to bear -- though media, through internal communications and even through congressional hearings. And yes, it does convince a lot of people.
Yet all of the above fails to constitute
scientifically viable evidence. From the existing body of evidence, UAP footage, radar data and other
physical records represent evidence that best lends itself to reliable scientific scrutiny, while not entirely dismissing first person accounts.
However,
the low information content and high interpretability of these physical records render them far too open to speculation, poor for scientific verification and ultimately unimpressive as evidence.
That UFO theorization invariably, throughout history until this very moment at the Capitol Hill, concerns itself with low quality evidence, is to be expected from any exercise requiring a lot of speculative latitude.
