They thought of just about everything. They knew a time like this time would come.
It’s because they understood history and history clearly shows that people and power do not mix well. That’s why the Constitution is a limiting factor on government (a document of negative rights) and not an enabling factor (a document of positive rights).
The founders understood the paramount importance of defining what the government was allowed to do while expressly saying it was not allowed to do anything else. They understood powerful people very well and the powerful people’s mindset has not changed. That’s why the arguments they made 200+ years ago apply to today and they seem prescient.
The tools and trappings of man has changed but the nature of man has not.