At first sight, the decision to insist on keeping a provision that benefits some of America’s wealthiest people seems a far cry from the concerns of voters in Sinema’s southwestern home state of Arizona.
However an FT analysis shows that the senator is a beneficiary of significant contributions from the private equity industry — whose lobbying machine and political influence have grown increasingly powerful over the past two decades.
Other sources:
https://theintercept.com/2021/09/26/kyrsten-sinema-private-equity-tax-loophole/



System Justification Theory explains this well. People support existing structures as a way of limiting cognitive stress. Political conservatism (and I don’t just mean this in the American sense) is also a defining cause of this. This can manifest as general apprehension towards radical systemic/social change.
But this isn’t something that has existed for a long time. This has only become an issue since citizens united vs FEC in 2005