What event led to the end of the Middle Kingdom?
The Hyksos took control of Egypt
If you mean Egypt, then there was an increase in the power of Nomearchs. Nomearchs were the equivalent to middle age nobility. This led to a decrease in the power of pharaohs. This happened because lots of fertile farmland was being used by older previous pharaohs that had died. The produce from those farms were used for upkeep of the respective pharaohs temple complex.