Disagree with your statement. I am in cryptocurrency since long.
Never heard if any trader have gone bankrupt. You should present some data if you you are are saying. Rest if its true, there must be only reason lack of appropriate knowledge or lack of cryptos understanding. These are the only reasons if someone faces loss in cryptos.
I dont think he was referring to investors, I think hes only referring to the exchanges that have gone bankrupt. There are many of them, thats why its good to know what exchange youre investing your money on so that you dont end up losing it. Some of them are scam and after raising the amount of money they need, they close down and zoom off with investors money.