In my headcannon, Tarzan react this way for Mufasa be an uncle figure. Mufasa knew of humans but accept Tarzan for his virtuous heart.
Also, Jane Porter sees this scene by visions. She forgot it was visions ,and try to save Mufasa from Scar. She got sicken by Scar for his betrayal and his lack of morals. And cry for Mufasa and Simba. And by doing so, she prove to many she,was as virtuous as Tarzan. And she meets Mufasa who thanks her for saving his family from poaching.
Also, Rainbow and Fluttershy react as Jane. And get to meet Mufasa.

Mufasa’s death was so sad. He risk himself for his son, proving a real papa. And he was betray by Scar, his own brother.