Every time a rich person loses money, I think of it as karma for abusing loopholes to pay less taxes.

They were attempting to shortsell certain stocks, including Gamestop – which as I understand it, means selling stocks they don't technically own at a set price, then buying the stocks later, hoping that the price dropped in the meantime so they make a profit. In essence, betting that the stocks will lose value. However, a bunch of redditors started buying these stocks en masse, driving the price up, forcing the rich people to spend massive amounts buying stocks they've already technically sold for a low price.