It was time to crown Sugriva as king of Kishkindha.
"Noble Rama," said Hanuman, "we ask you to come to the royal city and conduct the coronation ceremony."
"Dear Hanuman," Rama replied, "by my father's order I may enter no city or village during my exile. I will stay here on Rishyamukha Hill with Lakshmana, awaiting the end of the monsoon. Then we must rescue my Sita!"
"I will come as soon as the monsoon season ends," vowed Sugriva.
So Hanuman and the monkeys went to the city where they made Sugriva their king, with Vali's son Angada as crown-prince.
Inspired by: Valmiki's Ramayana
Notes: This is from Book 4: Kishkindha Kanda, sarga 26.