I can understand not convicting him of murder. But pulling the trigger of a gun on a crowded city street surely qualifies as involuntary manslaughter, which only requires the death come thru an act a normal person would understand could be dangerous to others.
The pistol he fired requires a 10 lb trigger pull to fire the first shot. No one does that “accidentally” - although in SF, no one on the jury may have ever touched a gun before.
If you ask me, the jury let him off because they wanted to stick a thumb in Trump’s eye.
The politics of it is far more important than Kate Steinle.
In liberal theology, guns simply "go off" by themselves all the time. It's reasonable to assume a San Francisco jury would lack the knowledge to understand what you just explained, without detailed instruction from one of San Francisco's Kamala Harris-like prosecutors, who wouldn't know either.