I choose to believe that Margot Robbie has actually decided that shitposting on Lemmy is a worthwhile use of her time, and we've all just assumed this is a shitposter.
The difference to YouTube is that it's not intended to create a huge platform centralizing videos from the whole world on a single server farm (which is horribly expensive).
From their website. It's a very different system, and also not funded by advertisers, which means someone else has to pay the bills.
Yeah, these types of "pranks" often reek of jealousy.