The Founders didn't create a democracy. They were very clear about it ... they founded a republic ("if we could keep it") with democratic features at the state and local level.

Why would they do that?

They'd studied the governments of other countries, particularly in antiquity, and identified their weakness. Democracies always start out well and inevitably end up with the majority crushing minorities and the population centers crushing the rural districts that produce everything the cities require to survive.

There would have been no United States had they been aiming for a democracy. The small-population states were unwilling to be enslaved to the more populous states. And, so they chose a republic composed of states that featured republic forms of government, chosen by democratic means, within those states.

So, I guess we've now reached Franklin's warning - "If you can keep it". Fortunately, amending the Constitution requires cooperation from the states.