You can turn activation lock off only by entering the correct Apple ID/password combination. The correct combination is the one allowed by the person owning the device. If this combination cannot be entered, then the iPad is useless to you unless there are extenuating circumstances (e.g., you have the receipt for your purchase of the device with its serial number on it or a court order instructing Apple to assist in the provision of access to a decedent’s information from the deceased person's accounts--(see How to request access to a deceased family member's Apple
accounts https://support.apple.com/en-us/HT208510) If you have either, contact Apple support using one of these
options.
Get a call from Apple support to help solve your problem using this link https://getsupport.apple.com/?caller=kbase&PGF=PGF63005&category_id=SC0245&symptom_id=23362
Apple ID Support https://support.apple.com/apple-id
Apple ID account security for country-specific and region-specific help https://support.apple.com/en-us/HT204169
Get Support: We’re here to help https://getsupport.apple.com/. Go through the options to find the best support option.