Patton , as a result of the accident, had a broken or dislocated vertebrae in his neck. He was totally paralyzed from the neck down. He died from complications of that severe injury. Remember this was 1945 and even with present day medical care actor Christopher Reeves(SP?) died from a similar injury. An motor vehicle crash used as an attempt to assassinate a person is an unlikely method for use as a means to bring about a man’s death.
I agree with your comments, I’ve read a lot of books about Patton and the circumstances of his death are well detailed.