A division with UCLA, Berkeley, USC, Stanford, UCSD, UC-Davis + plenty I'm forgetting would be instantly watchable in football and basketball. Really the only thing they'd be missing out on would be March Madness (a big deal) and the college football championship (a minor deal). There would be a very swift Rose bowl replacement, and I'm sure the invited BIG10 would be happy to attend, and if not for whatever reason a top 2 from that division would be a fun championship game too.
Really I see the only blocker here being participation in March Madness- but that feels like a short term roadblock and 'lets figure out when to pull the trigger' situation rather than an impossible hindrance.
The smaller sports will certainly suffer in the short term- but California is a massive market and having a California only college league is totally plausible.
Absent legislation with more teeth or a broad coalition of states and schools from across the country, I highly doubt California schools will drop out to create their own league. In fact, the money they're looking to give to athletes will soon dry up, absent the lucrative contracts the NCAA holds. Who would watch an independent league with so few teams in it and basically no national tournament circuit?
Far from forcing the NCAA's hand, I think Newsom just passed feel-good legislation which doesn't really change anything. Perhaps other states will jump on board, but there doesn't seem to be any sight of that at the moment.