Then imagine it's security is breached.
If this happens at a time when bitcoin has been mass accepted and it is a dominant currency to store wealth in world-wide - then a criminal could be in possession of half the wealth in the world.....
Sounds surreal and could not happen in a FIAT system.
I think if one wallet had half or more of the btc in existence, we'd already be in trouble, whether the wallet ever got hacked or not