A lot of my picks are already mentioned so I'll pick an odd one:
Air crash investigator (called Mayday in NA). It's dramatizations of the reports from air crashes, organized like a murder mystery. Surprisingly compelling.
I've never been nervous about flying but this show really underlined how safe flying is, it's actually kinda crazy how thorough the reports are and how often they lead to rule changes. I wish the same institutional dedication to safety was practised in other industries (especially cars).
Episodes that take place in the 80s have you face palming at how stupid the mistakes are, more modern episodes are almost always a combination of many many different small low chance events and minor mistakes from the pilot piling up. I usually skip the terrorist episodes though.