Because they did not foresee a Corrupt executive branch thoroughly corrupting the Legislative and Judicial branches. The plan of checks and balances they thought would protect us has failed miserably. There is NO PLAN B. In their ingenuous naivete they could not foresee a situation as the one that exists today.
So navigating will be treacherous and dangerous and the roughest part is yet to be.
They tried to set up a workable democracy which has lasted until now. No one knows what to do. The people who have the power to correct the flaws are flawed and corrupt. No recourse. Is insurrection all that's left?