This problem goes back to the 1980s as police forces were being upgraded because of perceived crime and drugs. As they hired more people....they didn’t really filter out the incompetent or unqualified or emotionally unstable guys. I’d call it the 66-percent-rule. We have 2/3’s of the cops in the nation who do a decent job and deserve some respect. The remaining 1/3 need to get themselves a guard job at the local mall and give up on being a cop as a career. It’s across the whole system....local, state and federal....even the secret service has hired losers.
Just as an aside: in Los Angeles, court ordered racially based hiring produced a considerable number of new hires who couldn’t meet the qualifications due to prior interactions with the criminal justice system but were then hired anyway by court order. Just another factor involved.