I have no real answers, but it could be that shitposting is something some use to decompress a situation. Like when two family members are heating up a pointless holiday argument and it starts to get awkward for those around them, so people make dumb jokes in an attempt to diffuse the situation. Then others may "change the topic" filling any dead air with even nonsense or something people don't overtly care about but it helps avoid the actual issue at hand. Which could assist those family members taking a step back and cooling off or maybe it allows them to not address the underlying issue and there will be underlying resentment in the relationship for a few decades.
Another alternative that the person above you may have meant, is that people don't want this space to die because some bad actors. If the main focus is that bad act, then people are more likely to drift away...