I think it's more that narcissists self-select into the police force because they like the power and control they have over others' lives, and it makes them feel good about themselves.

I suspect that the condo was just the flashpoint, and that Diaz was a "cluster B" personality type (narcissist, psychopath), manipulative, exploitative, entitled, sadistic, and lacking empathy. Narcissists see other people as "things" that are relevant only insofar as they are useful to them. When a narcissist loses their their narcissistic "supply" (which can be almost anything, e.g., a spouse, girlfriend, etc.), it can cause narcissistic injury and cause the narcissist to see their ex as the enemy and cause them to want to destroy them. A disturbing strategy is to try to destroy them personally, professionally, and financially, and drive them into a pit of despair so that they kill themselves. If the narc succeeds, it makes them feel important. In their minds they think "I was so important to this person that they couldn't go on living without me." They're highly disordered people that manipulate and exploit people. It's good to see one get caught.

We're talking about police, so why not both?

You own the phone, you own the person.

Okay, what if they did this with a device that's attached to you at birth, and follows you your entire life. It monitors every single interaction your entire life. Then you die, and the AI version of you lives on. It would probably be a pretty good approximation of you.