How do you identify a human leader?

I’ve found a lot of people who know are experts in their fields and have a certain level of charisma, but then when they move into a leadership position, it’s apparent that it’s not their strong suit.

They could be seeking a promotion without the desire to lead people.

They might think that they’re good with people but can’t handle the hard conversations.

They miss the technical work and neglect their direct report’s needs.

How do you identify leaders who can lead people? And if they’re not a good fit, how can they move to a place where they do fit without shame, loss, demotion, or defeat?