It may be worth reiterating at this point that iOS/iPadOS devices are not intended to be shared between users.
So as to sign-in to your iPad, it was necessary to first-sign out of your own AppleID. The same is true in reverse.
When signing-out from iCloud, you will have been presented with the choice to save a local copy of the associated iCloud data. If you chose to do so, this data will have been automatically merged with the iCloud data when signing-in to a different AppleID. The only way to remove merged data is to manually delete each item.
Be aware that personally sensitive data (such as your Keychain), Contacts, Calendar, Notes, Reminders etc. may have been similarly merged.