I never log out. I did happen to check my IP logins before I disabled the account, they were all from me, and there were no logins on the day of the strange activity on my account.
What I could have done it enable 2FA for outgoing transactions, kept my crypto off coinbase(which I learned only afterwards from Dr. Google), and deleted my bank account data from Coinbase when not buying any crypto.
If it was a cookie attack, it should log different IP from your IP logins.
But since all of the login IPs is yours, it's not a cookie attack. Maybe your PC is already monitored for a long time, and someone has full control over your PC without your notice. He might also have control of your 2FA that's why he can do everything he wants from your account.
It doesn't make any sense to me either. They left crypto on the account. Why not just steal everything? Did coinbase lock them out somehow? Was I attacked by a bot that doesn't read the account balance? All mysteries.
"Did your bank not attempt to contact you before confirming such a large transaction?"
That's weird if you still have some remaining balance and he didn't steal all of your funds.
According to this https://help.coinbase.com/en/coinbase/trading-and-funding/sending-or-receiving-cryptocurrency/available-balance-faq
Maybe your "Funds on hold" that's why the hacker can't send the remaining amount from your wallet.
Right now, disabling your account is the best move and better wait for Coinbase response and maybe it is just a bug or system issue.
I have a problem before from Coinbase I never receive bitcoins to my Coinbase account and found out my BTC is transfer to another address which is not mine. I tried to contact them about this but they solve my issue by refreshing my account and according to them it's normal that our BTC will not stay on the address we use, it will automatically send to their main address. So I think your issue might be a bug or system issue and refreshing your account will show you the right balances.