Here. Unfortunately they're all doing it because they know the voters can do nothing to them. They're either retiring or not up for reelection for 4-6 more years:
Richard Burr - Retiring in 2022
Bill Cassidy - Just reelected in 2020
Susan Collins - Just reelected in 2020
Lisa Murkowski - Up for reelection in 2022, probably knows she has zero chance.
Here. Unfortunately they're all doing it because they know the voters can do nothing to them. They're either retiring or not up for reelection for 4-6 more years: