Oklahoma probably isn't poorer than Massachusetts because it has voted for Republicans in the last couple of decades.

Oh sure it is. Sam Brownback ring a bell?

Trickle-Down hasn’t worked. It’s time for Middle-Out economics.
okpolicy.org - Trickle down hasnt worked its time for middle out economics

GOP confronts another failed tax experiment in Oklahoma
Associated Press: GOP confronts another failed tax experiment in Oklahoma

Kansas, Sam Brownback, and the Trickle-Down Implosion
The Kansas governor’s attempt to create supply-side nirvana in Middle America not only failed to grow the economy—it created a crippling crisis of government that led to a statewide rejection of his politics.
prospect.org - Kansas sam brownback trickle down implosion

Now before you say “Oh, well that isn’t “the last couple of decades”, it’s true, but if you examine Kansas you’ll find that this mentality of “government is always wrong” and “lift yourself up” goes back decades, if not generations.

“What’s the Matter with Kansas” makes a persuasive argument that Kansans were fed a steady diet of culture war issues, and when Republicans took over (from the remnants of the FDR coalition) they yanked the rug and voted for what we now call “trickle down” policies, while still flogging the culture wars in public. Sam Brownback was just the visible tip of the spear, stupid enough to acknowledge what they were doing, but it had been going on long before him.

Culture populism trumped issues like better schools, infrastructure investment, and so on to the point where Kansas is now among the worst performing states in the country - but hooray, it has low tax rates if you’re a gabaillionaire, not many of whom want to spend a lot of time in Kansas since there’s no there there. The monies that could have made it a more productive and equitable state have only served to enrich the lucky few and cleave the state into have’s and don’t have’s.

It’s actually the story of America, writ small. And it’s still going on.