Given the criticality of seniority, this suggests that hours are viewed as a more important input than being able to demonstrate skills superior to all those who are not currently captains.
Not really SIA, when a pilot has sufficient hours and seniority to be considered for a command he likely to first undergo a Command Assessment, usually a few sectors with a training captain and a Line Orientated Flight Training simulator session. Suitability will also be considered, if successful with the assessment and considered suitable for promotion the pilot will now undergo a Command Course which he will have to pass. Hours and seniority on their own are rarely sufficient to obtain a command.