That's because in general people tend to believe, what supports their overall assumptions. Therefore they do not ask for sources, if it feeds their assumption. In fact, they even often attack people who warn them, not to fall into a believe-trap, because being sceptical could invalidate their believe ("truth hurts", comes from that understanding, that personal believes and assumptions may be wrong and accepting to be wrong, takes lots of courage, is the harder way, than to believe, what we prefer to believe).

So whenever someone claims something here, DEMAND he also shows his source, so that you and everyone else can verify it. If someone does not do that, ignore him, no matter how well it feeds your overall assumptions! That's the mindset of investigators or researchers. Otherwise you are only a believer - and therefore an easy victim for false flags and shills. That way you can quite easily separate the charlatans from those, who have interesting theories and paths to follow.

And in case someone has no evidence: no problem! If he is honest, he will not claim it to be a fact, but only an idea, or thesis.