I can't exactly decide how to interpret these actions. In a way, I can't really find where any market fundamentals have been violated.
As far as I know, the scenario plays thus:
GameStop is a video game sales company dealing mostly in traditional "brick and mortar" stores. Their big move is buying and reselling used games. With most video game sales now being done online, and the software exchanged digitally, their market stands to dwindle. Dwindle it has, along with profits, of course.
This put the stock into a depressed state. Bankruptcies have been mentioned. Accordingly, seemingly hidden money, like hedge funds have "shorted" the stock. In brief, a "short" means you think the price of the stock will fall. To do this, you find someone willing to lend you stock that you don't own. Essentially, you "sell" that stock at today's price. You "buy" later when you think the price is at its lowest. Thus, you put back the borrowed stock and reap the profit.
A Reddit forum called WallStreetBets or thereabouts concluded that GameStop wasn't going to just die. The new PlayStation5 launch, etc, could easily provide them with a cash infusion for at least a little while. They started buying the stock. The price went up. As more readers of WallStreetBets saw what was happening, they got in on it too. The price continued to rise.
The risky side of shorting a stock is that, at some point, you have to replace the stock you "sold" but didn't own. Not every joker can short a stock. The brokerage house has to be comfortable letting you sell a borrowed stock - knowing you'll be good for the replacement, win or lose. This trust has its limits. As the hedge funds that shorted the stocks reached their limits of this trust, the writing was on the wall - they're going to have to buy the stock at a grossly inflated price whether they wanted to or not.
The WallStreetBets guys realized this. Even more money came racing in. By this time, the story was general knowledge. The stock had gone from 2.80 a share to over 500. Those in early were looking at hundreds of millions of dollars of profit. Conversely, those who shorted were looking at commensurate losses.
Acting on undisclosed or otherwise non-general knowledge to profit from the market is illegal. Deliberately spreading false information to cause a market manipulation is likewise illegal. Here, though, it seems a non-traditional thought process just happened to run into a perfect storm of those awaiting a mundane return on an investment. I can't see how this scenario would repeat on a generic security. Really, it seems that the short-sellers took an uninformed, too risky stand and got blasted for their complacency.