Specifically: US military/intelligence/congress has historically treated UFO activity as highly classified. That’s now changed. Why is that? I don’t know. One candidate explanation:
1. Historically, some amount of “UFO” activity was actually classified, known US military/Intelligence programmes. Making the information public would compromise those programmes. So, in reality, the sightings related to identifiable flying objects. Just that they were identifiable by a small number of in-the-know people.
2. Things have changed. Some other actors - let’s guess Chinese/Russian - have stepped up their own secret programmes. Those items are now legitimately “unknown” to US authorities. If you’re from the US, that’s bad. Your putative enemies have something you lack knowledge of.
3. How to respond? In a world where the sightings are your own secrets then a strategy of silence makes sense. In a world where they’re not, the game is different. In this case, you want publicity: to cast them as unknown, (a) because it creates interest (/fear) and (b) tacitly lets your enemies know that you know they’re up to something.
That might be way off base. But the about-face in strategy is at least as interesting as the sightings themselves. I haven’t seen that covered elsewhere. Interested if anyone else has ideas/links.