Answer :
Bharat is characterized as a substitute king, the passage communicate that Bharat request to his brother Ráma to assume the reign of Ayodhyá, but he refuses to do so, this is explained in the following phrase: "But Rama nobly chose to be observant of his sire's decree". According to this sentence, apparently Rama decided to respect his father desire of not being the king.
Bharat realized that his demands to his brother wasn't enough for him to be the king, so he left to Nandigráma where he could meditate and wait for his brother to return while he reigned Ayodhyá on his brother's name.