This is not censorship. It's another form of "people interested in X might also be interested in Y". It's something platforms do all the time.
YouTube is a strange platform in that respect, but if someone searching for the moon landing gets a conspiracy video in the results because it's popular I don't see anything wrong with YouTube including a snippet of verified information that relates to the query.
Under dictatorships it's common to claim that all conversations are allowed except fear mongering, spreading enemy propaganda and outlandish claims.
Over time the "Overton window" of what is considered not outlandish in public debate grows smaller. For example, during WW2 there were rumors in Germany about extermination camps that were dismissed as "crazy conspiracy theories".
Covertly manipulating the public opinion by suggesting some content instead of something else is easy to implement, effective and difficult to detect.