iPad is iCloud locked to a defunct address
You can present the original purchase receipt showing the serial number to Apple to have them unilaterally remove the lock.

The alternative is to revive the "defunct" account. Since Apple doesn't delete them, you can go through the password reset procedure to reclaim access to the defunct iCloud account. Once you are logged in to the locking account, removal of the lock is trivial.

Otherwise, bypassing the lock is not feasible.