The Founders left it up to the states to figure out how they wanted to nominate folks for president. Up until 1910 it was all done through probably even a tighter knit group of folks in a caucus and convention process.
The first primary where voters could participate directly was held in 1910 in Oregon - pushed by the Progressive Party.
What is wrong with me saying I don’t like it when the party picks candidates instead of the people?
It’s not a lack of uunderstandingz, or of history. It’s a distaste that it is still happening.