It's all about perspective.
Comparing SF county to LA county is apples to oranges...
LA county is huge. I've driven all over that county for work in the 1990s. It's easily twice the land area of Rhode Island or Delaware and then some. At 10x plus more population it's far more densely populated than either of those Eastern seaboard states... LA county has almost the population of the state of Ohio packed into a land area around twice the size of RI.
The SF Bay Area is Alameda, Contra Costa, San Mateo, Santa Clara, San Francisco, Marin, Sonoma, Napa, and Solano Counties.
Of those SF Bay Area counties San Francisco is tiny tiny tiny... literally almost just a tiny little bit bigger than the city of San Francisco. Considering that fact... the infection rate for that tiny high population density area is insane.
Enough of that lets talk about trucks some more.