You’re right, looks like he would have had to turn to his left, while backing, to avoid the tree.... guess he got distracted. The fire hydrant would have been the second point of impact.
I'm not sure what you're looking at, so I thought I would include this picture, again, in this same (it's there earlier).
To me, it looks like he would back out of his driveway (or maybe he drove out forwards...), and then would drive normally out to the main street. At that point, he comes to the fire hydrant first and then he comes to the tree.