The powertrain isn't secured to the body with anything more than a few socket head cap screws. And, between the body and the engine you'll find rubber.

Therefore, in a high speed crash, over 100 mph into a pole, the massive forces involved can easily shear the mounts between the drivetrain and the body.............and the drivetrain continues onward in its original direction toward the original destination, where the body remains firmly in front of the tree.

If you want to make the argument that a bomb lifted the entire drivetrain out of the vehicle and deposited it 200 feet down the road, the force required for that would leave absolutely nothing at the point of the explosion other than a crater in the ground. For evidence of this type of bomb, reference the Oklahoma city bomb where pieces of the drivetrain were found several blocks away and virtually no part of the vehicle was left at the point of the explosion.