as far as i can tell, whether you get a Pol Pot or a Ho Chi Minh is a matter of luck...
has anyone thought of ways to robustly get the right person in charge?
This seems like either a somewhat confused question or at least one that relies on some core assumptions I don't share. Why is "get the right person in charge" the right level of intervention?
Pol Pot's policies aren't indicative of his personal badness, they reflect a certain level of skepticism about expertise narratives that benefit extractive elites.
Expertise narratives definitely have an extractive component. (Medical doctors use law and custom to silence others' claims to be able to heal, but MDs are obviously not responsible for all healing, or only doing healing, and they ARE collecting rents.) If they are 100% extractive, then anyone participating in them is a social parasite and killing or reeducating them is good for the laborers. I think it's easy to see how this can lead to policies like "kill all the doctors and let teens do surgery." This naturally escalates to "kill everyone with glasses" if you are enough of a conflict theorist to think that literal impaired vision is mostly a motivated attempt to maintain class privilege as a scholar.
To get a better outcome than Pol Pot, we need a better theory than Pol Pot's, that's nonetheless responsive to the grievances of the oppressed. Therefore, we need serious grievance studies.
By contrast, Stalin really was more destructive because of personality traits - but he was promoted to power by a situation which systematically favored those personality traits. If you don't want Stalin, don't do Leninism! In other words, if you don't want government by the paranoid, don't create a steep information-asymmetry-based pecking order where everyone constantly has to prove themselves & is under suspicion of disloyalty or weakness, and then place a single individual at the apex.
At least not if people in the system get to pick the leader. Which they eventually will, as they're better at intrigues than the philosopher-kings are.