Why were medieval manors nearly self-sufficient?

They were nearly self-sufficient because the wealthy manor owners would have access to farmland and food thanks to their workers, and they would also have an army to defend them in case someone attacked. They were essentially like small states where everything was organized.

I would say it is because they were isolated from other manors. They had their own workers, servants. They took care of their own animals and they did not seek aid from other manors.

Where are the following questions