I don't think what the OP is suggesting is necessarily a conspiracy. Institutions are wary of people who risk their credibility with claims that catch a lot of attention but may prove to be false. There's some incentive to make claims that capture a lot of attention and the field doesn't want to lose credibility.

If you think about how some scientists responded to speculation about Oumuamua you can see how they were nervous about speculation that could be sensationalized.