What caused FTX to downfall was because of the exchange shady things which Binance CEO at the time, CZ let people know about. So if an exchange is transparent and not misappropriating their users money or coins, there is no problem. What people want are transparent platforms that do not misappropriate users coins.
What caused FTX's downfall were Alameda Research's loans that used the exchanges' FTT token as collateral. The token did not have a very large and liquid market and when Alameda Research's overleveraged trades were going into liquidation, Sam began sending user deposits to Alameda to fund those trades.
There was a chance the downfall of FTX would have been avoided if CZ loaned money to Alameda to fund their trades, however, what did CZ do? He commanded the dump of Binance's share of FTT and announced that he will not help FTX heehehe. There was a fight between CZ and Sam already on social media before this.