Someone else logged into Twitter (X) using Apple ID

Everything points to your X account being compromised. You will need to check with them on how to secure your account and set up two factor authentication on that account. I see nothing that would show your Apple ID/iPad has been compromised. The only problem I see is that you use the same passcode/password. Never reuse passwords on multiple sites. Since that was done, I would recommend changing your Passcode on your iPad as well as your Apple ID Password.

Set a passcode on iPad - Apple Support

Update your Apple ID password - Apple Support

There would be no need to factory reset the iPad with the information you have provided.

X née Twitter has been having issues for a while. Instability, random follows and unfollows, moderation, etc.

If you did not re-use passwords, then this issue is isolated to your X née Twitter login. Re-secure that. Maybe add two-factor authentication over there, etc.

If you did re-use passwords (and did not use two-factor authentication on your Apple ID) your Apple ID may well gave gotten breached. (If you did enable two-factor authentication in your Apple ID, you would need to have provided an Apple ID verification code to any attacker here.)

If you suspect your Apple ID is breached…

Start here: If you think your Apple ID has been compromised - Apple Support

If you’re re-using passwords on your Apple ID and X née Twitter and potentially elsewhere, you’ll want to stop that and immediately remediate that. Don’t re-use passwords. Use unique and robust passwords. So-called password “cramming” — trying credentials leaked from some service breach ~everywhere else — is a serious problem for anyone re-using passwords.

Enable two-factor authentication if not already enabled, too.

Resolve any issues flagged in Settings > Passwords > Security Recommendations, as well.

Going forward: Don't reuse passwords. Especially, don't use the same password you use for your Apple ID for anything else.