The Creator Himself kills Pharaoh since he is the ego that was created as something from nothing. Only by the Light from the uppermost Sefira Keter can perform such a correction, and it symbolizes the death of the ego.
It is the last plague, which is the correction of the stony heart. From that moment onward Egypt begins to wither and not only in the spiritual sense but also in the corporeal sense.
Until then the Egyptians used to embalm mummies and build pyramids. Their corporeal culture was full of spiritual forces. We can say that they lived in the egoistic feeling of the connection with the spiritual world. But now they cannot restore their earlier desires anymore.
From KabTV’s “Secrets of the Eternal Book” 4/23/14