There are so many existential ways to view what happened to you and the other people involved that day, but I am sure you have heard them all by now.
What words of comfort can a stranger like me offer you right now? On some level I'm sure the older man's family was furious when the accident happened, and in their grief possibly made all kinds of assumptions and judgments about you.
That doesn't mean they were correct, nor does it mean your own self-judgments are or have been "correct." Can we ever know for sure? Probably not, but if freak accidents made sense then they wouldn't be accidents.
I once fell down a cliff because a well-meaning hiking partner tried to "boost" me over a tree stump. It was sheer luck and my youth that kept me alive. I have drowned multiple times an survived because I survived. There isn't necessarily more to it.
If I'd died, it wouldn't have been my friend or a lifeguard's fault in any grander sense.
As hollow as it may sound, this accident could have happened to anyone...on either side of the wheel. It is often the plethora of unknowns that seem to torment us most when something like this occurs. Letting go of them will only happen when you're ready and the time is right.
Until then, I sincerely wish you peace, freedom, and forgiveness.