It's not clear whether this was truly a hack (Coincheck) or the exchange was already insolvent due to a prior hack and the operator Francesco "the Bomber" Firano tried to cover up the whole thing with his tactics to blame the XRB dev team followed by forcing identity verification and stopping fund withdrawals.
Some interesting posts show there were several coding bugs in the exchange software which allowed for price manipulation by crashing the price through price manipulation. e.g. Apparently you could put in a 100K buy order at a low price, put in a sell order, and this trade would go through. This would tank the price and other people panic sell. There were probably many more glitches and exploits in their poorly-designed exchange.
Sources:
https://np.reddit.com/r/nanotrade/comments/7wklxm/bitgrail_hack_very_likely_came_from_btc_ltc_eth/
Sounds incredibly fishy the way that exchange was being run.
Amazing that it actually got big as is....the one that has me incredibly wary of it is Cryptopia.
-Its shady marketplace. (thats almost inviting a federal agency to grab that website based on this alone)
-how basically you can pay a fee and get listed...thats it.
-How difficult it is to take coins off Cryptopia or should i say how expensive it is.
Crypto right now is literally the Wild West.
thanks for adding to the discussion @lordprime