A lot of people are drawn to true crime because they think it’s educational - learning what not to do, learn about red flags, learn how to keep oneself safe.
Same reason a lot of people watch aircraft disaster documentaries while they’re afraid of flying. It’s not to get further scared due to the disasters themselves, but to learn what was done about the problems that led to the incidents.
A while ago I tried to look for something similar to Reddit’s Tip of My Tongue/Joystick (looking for media/games you have vague memories of and don’t know the title), but didn’t seem to find one. And I suspect it’s a bit niche thing.