They know full well how to handle their collateral requirements; that's exactly what they did! The idea that they "lost control" of the situation is pretty wild; how would they have exerted control over it? GME went nuclear in a day, and nobody a week before then would have told you it was going to happen the way it did. Should they require near 100% collateral from brokers on every trade, and everything that comes along with that? And no, them biting the bullet on trades that don't clear isn't a real solution. The ideal situation that would have mitigated it and kept them safe is same-day settlement cycles, but that's not a choice they alone get to make.

The LME situation and the DTCC/meme stock situation have very little in common, besides both of them being triggered by extreme price movement. It's much easier to argue that LME was rigging the game, but commodities are a different market that hit a little closer to home when things go bad. If the LME let short hedges get vaporized, the idea that they should have been left out to dry would be very unpopular in the fallout of that situation. Maybe they should have, but you're going to have a hard time convincing people not involved in finance of that.

Unless you are an institutional trader, the market isn't out to get you specifically. You aren't even shit on their shoe. You're shit three counties over, if that. They barely think about you. They barely even know you exist. You're background noise that most large players need to filter out to find out who is actually on the other end of the trade. Financial markets are rigged in the sense that big players will be bailed out and cut loose no matter what. They are not rigged in the sense that a retail investor can be on the losing end of a trade because they didn't understand what's actually happening.