Agree with everything you said as possibilities. There are clear proofs of concept that an accident can be caused by a compromised electronics, and multiple ways to do it. We can come up with endless possibilities, but I was trying to establish likely vs unlikely.

In his particular case, an attacker would require Hastings to be traveling at a high rate of speed to have a high probability of a fatal injury. Highland Ave is a 35 mph surface street. So the attacker would either need to speed the car up, or have him already traveling at a high rate of speed. If it's the former, Hastings could have just used the brakes. If it's the latter, there are lots of reasons why he could crash on a two-lane city street lined with trees and parked cars at 4 am. As you point out, it's possible a sophisticated attack could have also provided all kinds of distractions to prevent him from braking effectively.

I think the most likely explanation was that he was speeding and lost control, but feel free to disagree.