A great plan executed by the wrong people becomes a mess. A mediocre plan executed by the right people often becomes a success because the right people adapt.
So the first priority is character and capabilities: integrity, curiosity, and the ability to face reality. Skills matter, but skills are easier to build than the habits that determine how someone handles pressure, feedback, and uncertainty.
I learned to look for patterns. How does this person behave when wrong? Do they take responsibility or deflect? Do they learn or repeat? Those patterns predict outcomes more reliably than charm in an interview.
Putting WHO first also changes leadership. Your job is not to solve every problem personally. Your job is to build a team that can solve problems well, then place them in roles that fit their wiring. When roles match people, the organization becomes stronger than any individual.