Like many things Trump claims, there's a kernel of truth wrapped in a pack of lies. It's likely people in Trump's orbit knew about this (as the article highlights, it was visible to Congress), however what Trump claimed was pretty much nonsense: the crash was obviously
not caused by someone with "severe intellectual or psychiatric disabilities" in ATC.
I think the end of the article clearly sums things up: when Democrats had power, they didn't take deliberate, thoughtful action to resolve the real issues being raised. Because of that failure, we get to watch Trump take a wrecking ball after making DEI a thoroughly toxic issue during the election.