That's because they did think the elected officials would be so treasonous and corrupt, or to go so far away from liberty and freedoms.
They had no idea there was to be a monolithic conspiracy of traitors destroying the United States for over a 150 years plus.
They thought the militias and second amendment would take care of that before it got bad.
They thought the people would remove those people that were traitors ahead of time.
They were unaware of technology and how that has been used to control humanity and keep treason in the ranks that still goes unpunished to this day.