I think the main reason is money. Projects collected funds in crypto and when the price was falling, they didn't have enough money to create their products so they leave cryptomarket with the rest of investments.
If they are scammer then no need to list token even on exchanges.Wise scammers know the weakness points and then they attack to reach goal. They simply don't care about investors,exchanges etc..I think it is praising that scammers are smarter than us. They are the people who belong to this crypto world. As far as I can see, they only have a few tricks to make a living instead of trying to make a bit, and accumulate them
