Your confusion goes back to a lack of understanding the different between a pure democracy and the republic we have that is based on representation. The caucus system determines the will of the people in a superior manner through a representative chosen by small neighborhoods, who is dedicated to spend a lot of their personal time making sure the candidates are truly what the people want. That takes time and work that most people don’t have, but a dedicated representative can give on behalf of the neighborhood. Your analogy of a popularity contest is actually more accurate for the new signature gathering route or any democratic process where the people don’t actually know the candidate. People choose who they like based on passing recognition of a name, slogan or superficial reputation, instead of learning if they truly stand for what they say they stand for.