Taira no Masakado was widely revered as a just man and came from a big family so he was a candidate well suited for position.
Explanation:
Masakado was born into an influential family and had grown up to be the leader of the legions of Samurai and a powerful landowner. His influence made him one of the most powerful and well revered men in the country.
He led the rebellion and was able to sustain it for a long time as his people were fiercely loyal to him to the end. When he was beginning his revolt, a vast swarm of butterflies came to Kyoto and surrounded him, as if to show that he will be victorious in the upcoming battle.