Doubled? Consider yourself fortunate. Has anyone mentioned this? California just quadrupled.
From my understanding it's just very complicated but there are a few main factors.
The biggest one is, IMO, that for both home and auto insurance, the more expensive it is to resolve a claim, the more the insurance will have to cost for them to still make a profit. I don't know much about homes, but from the research and articles and data out there, in the past decade, prices of everything (both materials and labor) have gone up significantly. When it comes to cars, it's the same thing - parts and labor have gone way up. And, the cars themselves have got more complicated and more expensive to repair.
For example, let's compare my previous car, a 2017 Bolt, to my new car, a 2024 Prologue. Let's say an accident damages the front bumper, a wheel and tire, the windshield, and the side mirror. I have no idea if that's a realistic scenario but it's easy to compare.
Bolt: front bumper is just a bumper, windshield is just a windshield, it was a 17" wheel, tires were fairly cheap (and you could replace two to match), and the mirror's a mirror.
Prologue: front bumper has radar sensors. Windshield has a front facing camera for driver assistance which will need calibration, wheels are 19" so cost a bit more, tires are vastly more expensive and it's AWD so they need to all match so now you're buying four tires. Oh and the mirror has a blind spot thingy so I bet that adds to the price. It's also a lease and Honda leasing requires OEM parts to be used. On a used Bolt I financed the insurance company could have used aftermarket parts.
Now you can see why insurance for the Bolt was about $200/mo while insurance for the Prologue is almost $300/mo. In the end, I bet any repair on the Prologue would be 2x to 4x as much as the Bolt (plus it is also worth about 4x as much if they had to total it), so it's actually a better value to insure overall.
And for car insurance specifically, the amount of people without insurance is another huge problem. If an unlicensed, uninsured, illegal immigrant crashes into my car, and totals it, my insurance company will pay it, but who are they going to go after? The lease buyout is like $40K on my car, let's say that's how much it would cost them. And that's assuming I have no medical issues or anything. Now, if that same driver was properly insured... well, they'd be out nothing because the other persons insurance would end up paying for it. We need to enforce our laws which require insurance. A guy without insurance crashed into my buddy's Corvette and was like "omg I have no insurance what do we do" so my buddy called the cops. They refused to come because nobody was hurt!
In my mind, anyone pulled over or encountered in an accident that doesn't have insurance and/or license needs to be cited, have their license suspended if they have one, and have their vehicle impounded until they can provide a valid drivers license and proof of insurance. This would overall lower the cost of insurance for everyone.