No one really knows. The rationale in WSB is that they're trying to push a short squeeze. The other side is that this can be caused by retail investors flooding in.
The problem with the short squeeze narrative is that there just aren't that many shares shorted for that to happen.
What's more likely is that a bunch of the institutional investors haven't listed their shares on the market (thus giving the appearance of low availability), but the moment they decide enough is enough, they'll dump millions and the price will collapse. Retail investors will, as always, be left holding the bag.