For one, 4th is looking at property crime, not "most dangerous," where SF is #37 for violent crime. Yes, SF attracts the nexus of crime around the BART stops, but that also pulls it from most of the surrounding area, which OP was talking Bay Area as a whole.
Anecdotally, I've been here 30 years and never victim of a "dangerous" crime. Fat chance you move to Mountain View to work at Google and anything happens to you.
The only place in CA someone reading a "Best City for Techies" will encounter crime is Market St. and Tenderloin in SF. The rest of it in deep Oakland, Stockton, Modesto, San Bernardino, and pockets of LA, they will never end up.