Koresh was a kook, but that’s no reason to kill him or his followers who were just minding their own business. They weren’t a threat to anyone.
Let's cut this with Occam s razor shall we?
The BDavidians weren't a threat. No reason to burn a crime scene to the ground.
The 3 BATF, former Ark state troopers killed there were. Burn the crime scene to destroy any ballistics evidence, create confusion, and diversion.