I’m going to guess that the head doctor is NOT the actual villain here, but is more like the red herring. Like others are stating, he probably has some sort of probability-based Stand and is likely trying to collect the corpse of Christ in order to move it to somewhere it won’t cause as much mayhem as it has done over the years in Morioh.
I think Yasuho’s ex is likely the main antagonist here, and that he has some sort of time-manipulation Stand. Since Stands were introduced in Part 3, every main antagonist has had a stand that affects time. Dio, freezing time. Kira, going back in time. Diavolo, erasing time. Pucci, accelerating time. Funny Valentine, freely swapping between alternate timelines.