It turns out they were not needed at all to complete the evacuation effectively. A pointless waste. Neverthless once there the decision to turn around cannot be criticised, because driving on through an inferno even with a clear road is hazardous, tyres may puncture or explode, glass may shatter in heat, the coach would have been like a greenhouse, so any decision to proceed would be frought with risks which it would be unreasonable to take.
White House says circumstances of Taliban leader's death remain uncertain (Reuters)
from the article: Three victims of Carmel fire could have escaped, police report finds