Mufasa's backstory is explained in the new Lion King prequel, and it manages to make him completely different from Simba in the original story.

Mufasa: The Lion King confirms a key difference between the original ruler of the Pride Lands and Simba, who would come to succeed his father as king.

The Lion King offers an origin story for Simba’s father, Mufasa, charting his journey from an orphaned cub to the king of the Pride Lands. The film introduces a new generation of fans to the beloved tale,

This movie is as much about Scar, one of the greatest Disney villains, as it is about Mufasa, the title character. Read why.

Mufasa: The Lion King told a powerful story, but its own characters acknowledged that other stories, like Simba's Pride, could have come first.