Ugh these zombie ex-heroes can be a pain.
It was a mistake to re-animate them using the blue stones. I still think the former blacksmith should've just put it on the weapons or on an accessory so that the holy relics/weapons get to feed on the energy inside.
Apparently he was too late to save the heroes from their own weapons. He probably did his best to support them, but it was insufficient to save them from their own parasitic weapons.
So his research was on raising the dead. Not much choice left at this point.
Objectively, what he should have done was test the blue stone on one hero at most, check the progress and move on after checking for side effects. Like monsterization. Which it seems like it didn't even take long to show.
But we're back to someone who was emotionally unstable and obsessed, so rationality was probably out of the window by that point. This ties up pretty well.