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SEC think they are a regulator in crypto industry, they don't know that crypto is a decentralized system.
This doesn't really mean anything. If something would be truly decentralized they couldn't sue anything. There are always some form of centralized elements, especially with CEXes and with projects that launched via ICOS, IDOs or whatever money collecting method they have. They have a team to sue.
What are the problems with ADA, MATIC, and SOL?
If the problem is only about the significant drop in their prices, it is because most altcoins follow Bitcoin price. We must know that BTC is dropping its price to $25k again, it triggers most altcoins to drop again with significant changes. Moreover, we have bad news related to SEC vs Binance now.
From what i understand it's the method how they marketed their coin. You can't promise growth or even hint about it. Many of these allowed price talk in their official chats and even that's a big no-no to SEC.