Many of them went bankrupt because they could not choose a good coin, many also bought only because they wanted a high increase regardless of the quality of the coins they bought, and when the market went down the coin coin would go down even further, ending in cut loss. So the suggestion is that I buy coins that have a clear project.
To my opinion many of those who went bankrupt were too greedy and often took the loans for trading. So, the reason they went bankrupt wasn't the choice of wrong coins but the fact they didn't know when it's enough and when the conditions on the market changed they couldn't return the loans. Dealing with cryptocurrencies is not so simple and easy like many think and there is no guarantee you will make profit. So if you not experienced and snart enough you easily go rover the edge.