They are moving because red states are depressed. For instance, we have a huge problem where where people come from California after selling their homes and businesses. What we end up having is low wages, high food prices and people living in Vans and Cars (who are working) that can't afford even a 1 br apartment much less a house. We've been having that problem far longer than your depressed red states. What's sad is, we have had a bunch of California Republicans move here and they are friggin crazy. Hence the QAnon rep that was sent to Washington. We also have an increase in California Dems who are just as crazy. The Reps used to have a large majority but not anymore. The problem is, both sides of the new "Inputs" are crazy.
Democrats and Republicans move out of those states because of high taxes, over-regulation, and high cost of living. Businesses and residents are fleeing NY and CA. They are moving to Nevada, Arizona, Florida just to name a few. Normally that would be welcoming, however once they get to these states, they vote the same way they did that ruined the state they moved from.
For instance SF made a law that shoplifting was not a crime if the stolen merchandise didn't exceed $1,000. So why not go to stores and steal up to $900.00? The only way for the store to survive is to drastically increase the cost of products, which adds to the cost of living there. If Democrats agree with that policy, then that's fine. But we Republicans don't, so why should we have to pay those inflated prices for goods?
This is why we need to divide this country. Let Democrats run their states as they deem necessary, and let us run our states the same. I can tell you which country would have people deserting to get to the other side.