And it also good to highlight that majority of those have passed the so called security audit and yet there are still loopholes that wasn't found by this this independent security audits. We can say that it's not a guarantee of safety for this platforms.
Therefore, an audit is not proof that a project is completely safe. Even those that were hacked before, I’m sure many of them had already gone through security audits.
Hackers are just good at finding the part that auditors missed, and that small weakness is enough for them to exploit the whole system. As we can see, billions are being lost, so even big platforms are not completely safe.
The good thing is, as long as they continue learning from these mistakes, audits and security practices should also improve. Hopefully we will see fewer of these kinds of hacks in the future.