1. Their jobs are moving out of the state.
2. The taxes they pay aren't worth what they get in return for them.
Item #2 is important because people are actually prudent consumers when it comes to the "discretionary" taxes they pay. Most people I know aren't thrilled to pay high taxes, but if they live in a nice, safe town and their kids go to good schools then they are OK with it. In other words, they are OK paying for police/fire protection and public schools as long as they see the benefits of them.
What has changed here over the last 25 years is that they government has been collapsing into insolvency due to unfunded obligations to retirees. These people I described aren't willing to accept a scenario where they are paying high taxes to pay not only for the police officers and public school teachers in their towns, but for the pension and health care costs of police officers and public school teachers who retired years ago.
That’s true; the rest of the reasons given are symptoms of those.
I might also add that the leftism there is an attack on private morality and the family.
3) High cost of housing.