I can't see what credit has to do with anything. Evaluating the quality of the government they created has nothing to do with us maintaining it. Its ours (the living) not theirs (the dead). We owe them nothing.
Monarchy existed for 1000s of years. Longevity is irrelevant. It is never relevant who had the idea. Invoking the founders as a justification for anything is error. They are an arbitrary group of non-extants.
Why are you trying to connect the two ideas.