A lot of upset Californians want to secede now. The same thing happened in Texas in 2012. I know they won't actually leave, but I'd support letting them go. I think California is large enough to do it (so is Texas, but I'd like them to stay for their oil).
It would be interesting to see what new parties would form in an independent country of California. I suspect you would see the democrats dividing on racial lines like how they did in the Senate race. Harris won every group by far except for hispanics. Republicans would likely morph into a single-issue center-right party focused on rejoining the US.
That's a valid point, but Obama had numbers far higher than Trump has in California. And, to be perfectly honest, I personally would vote for California independence. But if the state were to ever leave, I couldn't really foresee a party movement to reverse that decision.
As to your second point, we may be seeing the buddings of something along those lines. As a state becomes a one-party state, the other party breaks down and the larger party grows to the point of having multiple factions. We're not there yet, but California has seen the Democratic Party registration grow from about 8% (or 1.3 million) in 2003 to 19% this year (about 3.7 million voters). With the Democratic Supermajority back in place, we'll have to see what happens.
TBH, if there had been a Republican senatorial candidate, more Republicans would have been willing to cast a ballot...
I don't know about that. How many people do you know that would actually think that?
If you compare apples to apples, Hawaii without write-ins and California without write-ins, California is indeed the most Democratic state in the nation by a very slim margin.