One is a company with a nearly $100 billion valuation using someone's likeness for their own commercial purposes in a large-scale consumer product, which consumers would plausibly interpret as a paid endorsement, while the other seems to be an amateur hobbyist nobody has ever heard of making a parody demo as an art project, in a way that makes it clear that the original actors had nothing to do with it. The context seems pretty wildly different to me.
I'm guessing if any of the Harry Potter actors threatened the hobbyist with legal action the video would likely come down, though I doubt they would bother even if they didn't care for the video.