What french king was know as the SUN KING?
Louis the 14th
The sun going down in The Lion King is said when Mufasa compares his reign as king along with Simba's towards the sun's position in the sky. He says "One day, Simba, the sun will set on my time here and will rise with you as the new king." So, basically, Mufasa compares the end of his reign towards the sunset.