Note that in the video of the crash fire, there is a gusher just ahead of the tree. That has to be a fire hydrant smashed off, causing damage to the underbody and gas tank prior to hitting the tree.
It would help if someone who knows the street there could verify or refute the presence of a hydrant there. Most of the visible damage to the vehicle is to the front. If the vehicle had hit a fire hydrant, the engine should have been shoved more underneath the vehicle, not launched down the road.
Also, a gushing water source would tend to spread the fuel more (gasoline floats), not leave it in a puddle under the vehicle.