Not surprising at all. The original case establishing Qualified Immunity wasn't about mere police officers - it was about a state judge, and only by extension local police since they followed the judge's order. The main decision was giving state judges all but unqualified immunity[0]. When you give a group of people power to do almost whatever, it's not a surprise the bad apples stay and multiply.
[0]
https://en.wikisource.org/wiki/Pierson_v._Ray/Opinion_of_the...
https://en.wikisource.org/wiki/Pierson_v._Ray/Dissent_Dougla...