[nothasan]

I think Google needs to add a better way to secure old / previously inactive accounts. My guess is because your account was old, and your current device, IP and overall fingerprint was different it decided you were an intruder.

[carbocation]

This seems inadequate to explain the removal of security keys. Unless Google inferred that OP was not just a garden variety intruder, but some sort of advanced persistent threat that had added such keys long ago?

[nothasan]

Yep I don’t know what’s going on here. OP posted another reply with the time they added their keys and they aren't recent.

[marcinzm]

Removing pre-existing security measures due to suspicious activity seems an odd strategy.

[nalllar]

I don't know, while this account is old and fairly infrequently used I normally have it in the google account switcher dropdown logged in rather than completely logged out.