The constitution explicitly recognizes that direct democracy decays to mob rule, which is why there are three co-equal branches with very different selection methods and leadership structures responsible for checking and balancing the powers of the others.

The problem they didn’t account for was the accumulation of such absurd levels of personal wealth that can be used to corrupt members in every branch to collude against the checks and balances they’re responsible for maintaining. Fk extreme wealth and the degeneracy that is required to create it.