This is a fun exploration, but there are just so many plausible additional factors, from population density, to SFPD's selective enforcement, to many others that can be at least as significant if not more so than this one.

This is not meant to be an exhaustive causal analysis. You try to control for land mass, but don't really mention anything else that might indicate elevation to be a less significant factor and I think that does a great disservice to what otherwise is an interesting exercise.