The catalyst event happening is apparently an impending "short squeeze" for GameStop (GME) stock. The underlying issue is being painted as a power struggle between individuals ("retail investors") and hedge funds / institutional investors.
The idea of the short squeeze is that institutional investors short-sold GME, meaning they took money in exchange for a promise to deliver shares later. This seemed safe because they thought it would be easy to buy cheap shares later and deliver as they are supposed to.
However, the share price started going up. People know the holders of shorts will need to buy back shares, so people (wallstreetsbets people?) buy the shares first. This drives up the price even more, increasing the potential desperation of the shorts-holders, and this cycle can theoretically get really vicious really fast, leading to a "squeeze". So retail investors are hoping to make a bunch of money off the institutional investors holding the shorts. In theory, if everyone bought Gamestop shares and refused to sell, the holders of shorts would be failing to fulfill their contract and be in huge trouble (but they will pay big prices first).
This leads to the David-and-Goliath story. The claim is that institutional investors are actively trying to paint reddit as market manipulators, in an attempt (either short or long term) to get regulators to shut down individual investing and tilt the field more to institutions. This narrative is aided by WSB trends to invest as a block in "meme stocks".
On the other hand, redditors are painting the institutions as serial entrenched market manipulators who got caught with their pants down in this instance, and who are trying dirty tricks to get out of a sticky situation.
Did I get it right?