The issue is not so much in hiring, it's in supervision and discipline. The culture needs to change to not tolerate sexist banter, to not cover up minor wrongdoing that leads to major wrongdoing. But changing culture is hard, because the people who have to do it are the senior leaders, who rose through the ranks in the middle of exactly that culture.
I don't think the police are hiring convicted criminals, or even people who have been close to being convicted of serious offences. But I'm not sure how we can weed bad people out in advance, if they have no previous record. We can't look into people's souls. There are no foolproof personality tests that will tell you if someone is significantly more likely than someone else to abuse their power.
To some extent the job of police officer, like some other jobs that involve dealing with people, will attract a percentage of the wrong sort of people. But then, we also expect the police to be streetwise and to be prepared to use force, if necessary. Statistically, the people who meet that description are probably more likely to have a tendency to commit violent crimes as well.
And we need a lot of them. We could have a 5-year probation period with an office's every move followed by a partner or with daily replays of their bodycam footage, but it would cost a fortune, and it would probably put people off applying. There are all kinds of ambiguities and tradeoffs.
So I'm afraid that these kinds of stories will continue, even if we do manage to fix the culture (which will be hard). I think about the best we can expect is that we pick up the bad people earlier, after they have committed one offence and not several. And maybe we can do something at the level of society or education to make men less awful, because ultimately, these offences are basically "men as usual", just with added abuse of official power.