I think Avi Loeb is legitimately excited about this topic. He's also aware that the public is tremendously excited and inspired about the possibility of UFOs, alien flybys of the solar system, etc.

I think he's achieved professional recognition, paid his dues playing the game of academia (very successfully), and is now pursuing things that he finds most exciting. The man has co-authored a thousand papers, literally, so I doubt he'd get much marginal excitement from hypothetical paper #1001, i.e., another instance of fitting a curve through noisy data to build support for an obscure model that very few researchers care about.

He has also pointed out that it's an invitation to ridicule in academic circles to talk openly about UFOs. He doesn't care though (why would he?), and that for sure is triggering folks who take themselves very seriously.