World was not aware of crypto currency until 2017. No one consider it seriously and that is why many criminals took advantage of that because it is decentralise and no one is controlling it. But like many countries are working on it this issue will get resolve in couple of years .
There's so many scams happen in 2017 particularly coming from ICO, however in the past, there are already a lot of recorded crimes like exchange gets hack, the most popular in the early times is the Mt. Gox hack which at that time, it's the biggest exchange who controls over 70% of bitcoin transactions that time, that is according to
https://en.wikipedia.org/wiki/Mt._Gox.