California is the bluest of the blue states and whatever happened there during the last 2-3 decades can be solely attributed to the policies of the Democrat party. Else how can a state which is home to the Silicon Valley can become bankrupt? I am not defending the GOP as well. Pre-Trump era Republican party was like Democrats on steroids. There were countless invasions of third world nations, which resulted in military expenses of trillions of USD. Trump era was an exception, as the tax rates went down, and there were no major military interventions.
If you google "best places to live in the USA" you will see that majority of it is democrat cities, and if you check where people are moving to, that's mainly blue states as well, with one exception which is Californians moving away. What you need to understand is that Sillicon Valley didn't made it better, it made it worse, it caused wealth discrepancy which caused people who are not as rich to move away from there due to lack of money, that's the reason.
Trump or no Trump, democrat or republican, black or white, religious or secular, like I said, it's NEVER about the ideas, it is always about the people, good people will create good states, bad people will create bad states, simple as that. It has absolutely nothing to do with which party you are on.