They knew better; they knew it would get worse over time. We now live in the worse:

"The first man put at the helm will be a good one. Nobody knows what sort may come afterwards. The executive will be always increasing here, as elsewhere, till it ends in monarchy."

–Benjamin Franklin, at the Constitutional Convention, June 1, 1787

The other problem with the Constitution is that it’s purpose is to protect the opulent minority from the majority.