The Bolian named Chell was a Maquis engineer who got sucked to the Delta Quadrant along with his crewmates and ended up on Voyager. He was generally portrayed as loud-mouthed, rude, and lazy. He was one of the five candidates for Tuvok's disciplinary program in episode S1E16 "Learning Curve", and still hadn't completely accepted his role in Starfleet by episode S7E04 "Repression", which takes place six years later. In general, Chell was considered by many to be the epitome of what a Starfleet crewman should NOT be.
Yet, when Tuvok began accepting applications for the new Hazard Team in 2376 (a full year before "Repression"), Chell applied and was accepted with a promotion to Ensign. The Hazard Team was designed to be an elite response unit which could easily be responsible for the lives of everyone onboard the ship.
Given this crewman's past & overall attitude, what possible reasons would Tuvok have had to accept Chell as a Hazard Team member, let alone with a promotion?