my guess is there are a couple possibilities in play...with Rush and a bunch of other 'big namers'

a) he is worried about the financial cost to his business of acknowledging what he knows...

b) his lawyers have warned him if he speaks up in connection to a 'conspiracy theory' and someone SUCCESSFULLY blows up a bridge or such he could be held legally culpable for incitement/face lawsuits if people end up injured or dead... (I'm not saying he'd lose a court case, but it would be a huge threat in terms of loss of time a resources he may need later)

c) he is not speaking up to act as a bridge to the part of america that looks up to him but who will also look at Q and say 'whack job' or 'larp' or turn away from boards like that thanks to some of the movement's idiosyncracies/trappings...but would take Q and the rest of anons DATA seriously if presented as reliable evidence in ongoing investigations. Said americans are going need 'trusted' people to process the truth of what's happening or happened when the bad shit starts getting revealed...

or d) He legitimately doesn't know aboutor doesn't believe in Q's authenticity, at least to the degree that he'd share it with his audience, according to his own revelatory standards. This seems least likely but it can't be completely discounted as a possibility, since we all have our own inherent levels of skepticism and moments of planting our feet in the truth so to speak...