Not surprised at all. Exchanges are completely unregulated and while they do provide a service, they can also do whatever they want with "inactive" fund, whether to invest in other structured investment products, high risk investments or just themselves (aka embezzlement). And this should be seen in the context of the high risk - high reward crypto space as well.
My only advice is to go in with your eyes open; there's never a perfect risk free world, and by choosing to be in crypto, you have just gotten into one of the most high risk investments in terms of potential fraud, regulatory risk, exchange risk etc. This will eat people alive who do not do their own due diligence, while there are high rewards to be made for the brave and continually informed.
And that's kinda fair in the long run.