Despite all the (phony) reverence for the document in the U.S., the Constitutional Convention fucked up, badly. The Founding Fathers disliked political parties, considering them divisive, so they drew up a system that assumes that all office-holders are independent. That system is supposed to leverage the mutually-opposing interests of the representatives to check and balance each other. It simply can't work if a group of people with aligned interests control multiple branches of government.

They signed their new constitution in 1788, and by 1792, Alexander Hamilton formed the first political party. Whoops.