I would suggest you look a little deeper. It's not like politicians were surprised; they KNEW. However, the entire game was predicated on inflating the number of unqualified voters. Hence, the various voting enfranchisement acts dating back to the Civil war and continuing apace to this very day.
Policitians and the power elite who back them generally possess above avg intelligence. It's not mystery to them that democracies have repeatedly failed throughout history. So the challenge was to convert the republic into a democracy. Once that was achieved, anything is literally possible, as we witness on a daily basis.
The only way out is a reset. It's coming sooner or later (what, you thought the USA would live forever?); when it does, a couple of hundred years of tradition are going to go medieval on usurpers.
I do not know if all the politicians knew the implications of their policies. Certainly, some did know. No one, politician and voter, is without blame. I do not excuse myself from this list. People were programmed by the federal government and by government schools that the government could provided for all their needs with little or no cost. The politicians and special interest groups all wanted power and money, and they were willing to lie and deceive to get what they wanted. I truly wonder that if a political candidate ran on telling the truth and preaching limited government if he would be elected to a national office? I doubt it.