I was reading about Cashaa, that was hacked and 336BTC were stolen. But the hacker can't move them right? He will leave footprints. So why should hackers steal them since they can be found? For example if they want to convert them to fiat.

The only way I think you could get by from this felony is to keep them on very long term. So long that it may be forgotten. But still, it may.