<a href="https://www.coindesk.com/crypto-traders-who-lost-big-in-poloniex-flash-crash-receive-bitcoin-refunds">Poloniex gives refunds to customers</a>

When stories like this gets posted I always ponder to those who stolen or did the act of scamming others and gets away with it is a win win for them. As they get what they want and have people who they stolen from feel not as angry as they get back what is stolen from them. Although Poloniex would suffer some lose for paying back the customers.  Still not often is this done where exchange pays users for loses even though trade occurred. 

The key dynamic for the significant drop was due focus lack of liquidity. Same holds true outside of crypto exchanges. In general anything that is traded with lack of liquidity will result in dramatic price swings. In time hopefully there will be enough liquidity in the exchanges that these type of incidents do not occur.