Specifically - "Although firefighters had earlier drenched the building prior to the bombing, after the fire broke out, officials said they feared that MOVE would shoot at the firefighters, so held them back.
Goode later testified at a 1996 trial that he had ordered the fire to be put out after the bunker had burned. Sambor said he received the order, but the fire commissioner testified that he did not receive the order. Ramona Africa, one of the two MOVE survivors from the house, said that police fired at those trying to escape"
From the links, 60 neighboring homes burned down from it, no fire department presence. So...regardless of the reason, "the fire was allowed to burn".