Or, the FBI may know who Cooper is, but they were waved off from naming or charging him because of Cooper’s intelligence community ties. Per investigative reporters and an acquaintance who was an Assistant US Attorney in South Florida, in the 1970s and 80s, there were a number of Cuban intelligence operatives and assets who had near categorical immunity from prosecution because of their work for the CIA and military intelligence. For years, they played havoc by running drugs, laundering money, and taking over and corrupting banks. It is easy enough to imagine DB Cooper as having achieved a similar sort of immunity.
That's part of the claim -- that he was ID'd by some plausible-denial freelancers who told him he'd have to work for them or go to prison. Apparently the evidence offered by the author is a pile of passports and fake IDs and diary entries by the suspect. BTW, those who watch the video may be struck by the total lack of reaction by those in attendance. Number one, there probably weren't hundreds in attendance, and number two, Grand Rapids audiences are a little more reserved than are those found elsewhere in the country. Except when Trump is here of course.