How and when did Tennessee become worse than Texas and Florida?

When Haslam retired. Which he did because he saw the writing on the wall that there was no longer a place for him.

Haslam wasn’t good, but as a corporate lackey, he just wanted to keep the machine running, he wasn’t ideologically committed to all the christofascist culture war bullshit, and would push back on it when it would rock the boat too much. For a few years, he held back the rising tide of fascism and the state was less bad than most of its neighbors. But as soon as he left, there was a massive wave of legislation making up for lost time. The people running things now are fascist idiots, whether ideologues or opportunists, unrestrained by conscience or reason. If Fox News runs a story about something, there will be legislation about it within a week.

How did things get this bad? Because the corporate lackies created the material conditions for it. They were happy to work with and spur on the christofascists because it gets them voting Republican. And now they’ve created a beast they can no longer control or restrain.