From all of these suggested possibilities, I do admit I saved the seed in my google drive. To access my gmail account though, requires 2FA. Google did not notify me for a remote login etc. I used the same seed since 2017 on the same ledger device.
It's never advisable to store your seeds or private keys into cloud storage such as google drive. That's probably the reason why you've been hacked. I thought about when you've access on the public wifi, maybe there's also something to do with that as it's also never advisable to do that with your laptop that you use to access your funds.