SSR
Why do you keep mentioning the fact that it was near Santa Barbara, or that there were nearby Mil airfields????, are you questioning the flight crew decision to return to LAX?
If you look at the flight details (on Flightaware) they had just reached FL360 at 09:12 and diverted, starting descent at 09:14, at 09:25 they were at 10,000 ft, and on the ground at 09:45.
Santa Barbara does have jet traffic, but not 757 size, mainly RJ's, turboprops and bizjets.