One of my hunches is that Jesus, if he ever existed, and if the bible is based on somewhat real events and isn’t just straight up allegory (two giant ifs), was deeply wounded by the crucifixion but not quite dead when he was removed from the cross. Then he sat around for a few days, somewhat recovered from his wounds and addressed his supporters (a.k.a. “was resurrected”), and then died a few days after that from infection or other delayed causes stemming from the crucifixion.

EDIT: People were notoriously bad at determining whether or not people were dead until the advent of modern medicine.