It’s always been an oligarchy. At no point were the masses in charge of the US. It was founded by rich, landed gentry from Europe leading the common man to battle under the banner of liberal values, but they formed the entire government to be by of and for the land owners. They even gave MORE power to land owners who also owned people. That’s how committed they were to oligarchy from the beginning. It’s always been a structure by which the elite manage their affairs including how best to prevent a revolt by the masses.