As the protagonist, you are the leader of your kingdom. High Charisma naturally boosts your Persuasion skill, which is vital for succeeding in many game-altering dialogue checks.
Why the Inquisitor? Because it mirrors the game’s own philosophy. pathfinder kingmaker best starting class
This version deals massive extra damage to enemies of a different alignment (which is most enemies in the game). As the protagonist, you are the leader of your kingdom