The perfect theft in crypto is claiming that a project or an exchange is hacked when its all an inside job, the reason why I think about this is I have never heard about other top exchanges helping a exchange that just got hacked to track their funds and get some back at least but if it's a sole hacker from outside they will track him or them down, why is that?.
This is something that I have always suspected, without a doubt hackers are very capable of stealing from centralized exchanges or from coins which have holes on their smart contract, however it is also very possible that a number of those supposed hacks were instead inside jobs so the developers could blame someone else while at the same time they try to appear as the victims when they are the perpetrators of the crime, however it is not possible to know how frequently something like this happens and we can only speculate about how common something like this really is.