After the iPad has been removed from your AppleID account, it is impossible to remotely manage or erase the iPad.
While you will be unable to erase the iPad, this is perhaps not as serious as might initially appear. Unless the iPad can be restarted to a running state - and the Passcode known only to you is successfully entered - neither you nor anyone else will be able to recover any data from the iPad.
iPadOS uses an encrypted filesystem. Successful entry of the iPad Passcode unlocks the Secure Enclave (this being the iPad's security chip) within which the only copy of the encryption keys - that are required to access and decrypt your data - are stored. In the unlikely event that the iPad is ever recovered to a running state, there are a limited number of attempts to enter the correct Passcode before the iPad will become disabled.
As such, you have no reason to be concerned that any data stored on the iPad can be recovered.