What the hell is going on?

If binance falls, there will be something like a Domino effect for sure! How come an exchange is custodian its funds in another one?
No doubt, all our funds should be in a personal cold storage, a hardware wallet is the best for most of us.
Of course we should use a hardware wallet through which we can safely store our accumulated cryptocurrency. If binance ever goes down, it will certainly have some impact on the entire cryptocurrency market. However, in some cases the price of Bitcoin may remain stable where people will find it convenient to trade and people will actually advance there.
My personal opinion is that all Bitcoin or cryptocurrency money should never be kept in one wallet, the money should be divided into many wallets whether it is small or large.