There have been cases when hacked two-factor authentication?
Yes but mostly due to the user's action.
2FA is one of the most recommended extra layers to our online security because it really giving scammers a hard time to breached it even how smart they are. But instead of attacking directly the strong wall provided by 2FA, these scammers will lure their victim to a certain trick
e.g phishing, malware, etc. and when the said user falls on that trap, that's it.
Don't use gmail,which is not secure and no more privacy,google itself will sell your email to advertising companies so you will get lot of spam messages,better use mail like proton main which is end to end encrypted so you won't get spams also well as hacks.
Spam email messages are always around since the early days of the cyberworld. Although there are lots of questions about the reputation of
Google! being an email provider, I like how they evolve through the years starting from a small fry into a bigger one. I only received a few spam email messages from all of my Gmail Accounts on and the first spam email I received started when I use my emails in registering to a certain site. Therefore, not Google! fault in the end but through the other party.
And for their security, it's now difficult to breach a certain Google account nowadays. If the account owner properly set-up their security, there are tons of verifications first before a hacker can access the email even they know the password. Unless the hacker is just around the area or being a snake to that victim all the time.