How can someone hold that kind of money in a centralised exchange? Not to be harsh, but the person typically got what he deserved. Coinbase is one of the exchanges that can easily freeze users funds once they suspect anything or the 3-letter government agencies ask them to do it.
Even if you want to hold money in a self-custodial wallet, it shouldn't be centralised tokens/coins. The worst of it is tether; they can freeze your fund while it's in your private wallet immediately. The government asks them to do that because they are fully open to obeying and taking orders from them.
Maybe he was getting ready to sell. With the market being how it is now, it's clear that the macro is going to remain uncertain and so far BTC behaves like a leveraged NDX, so about 2 to 3x NASDAQ vol, about 6x SP500 vol. So if the market crashes a good 20%, then we may see a big crash on BTC and he wants to dump before that happens.
If you want to buy a nice house, you need to sell on an exchange that has KYC, because no bank will take your money otherwise. And so if you do this, and have some inputs that are blacklisted, it could be a problem. This is why getting paid in BTC and then wanting to use it to buy a home or anything that requires KYC is a risk because you may be holding blacklisted inputs and you don't even know it.