It happened because the consuls only cared about their own personal wealth and not for the people. The senate got richer and richer while the people got poorer and poorer. It ended with the rise of the Empire and the rule of an Emperor. The disadvantage was that all of the power was in the hand of a single person and often the Roman emperors were tyrannical.
People tried to abide by them and then realized how imperfect we all are, and they realized that we need salvation.
In reality the [peace] policy rested on the belief that Americans had the right to dispossess Native peoples of their lands, take away freedoms, and send them to reservations, where missionaries would teach them how to farm, read and write, wear Euro-American clothing, and embrace Christianity. If Indians refused to move to reservations, they would be forced off their homelands by soldiers.