Most of these "hacks" are inside jobs. They come up with excuses so they can easily run away with users' money. I've seen it time after time and it looks like this will never stop as long as there are greedy people in this world.
This scenario was also in my mind, I think it was an inside job because it is impossible that someone knows or great scammers knows the system used by these exchanges. I personally not having an idea why scammers got access to their system or unless it is an inside job.
But on another side, yes, scammers now get smarter and they waiting for an opportunity to get access to any accounts that having a potential to steal fund.