Why are there so many Mr. Nan Guo in the eight-character numerology, such as the land king, the guest in the cloud, the rainbow after the rain and so on?

After Mr. Nan Guo escaped, he searched everywhere for hiding place for a year, two years and three years. . . . . . How time flies! The money he earned in the palace soon ran out, and sometimes he ate the last meal without the next. He thought, if he had real skills, he wouldn't have to play in the band in fear? So he asked around about the bamboo blowing master. Finally, I found an old man on Mount Emei who was the founder of Cui. He waded through mountains and rivers and took pains to learn from his teacher. He learns to play the flute very seriously. If he doesn't understand, he asks. Every time he learns a tune, he practices hard. When he learns the next song, he always plays those old songs to the teacher, and even the teacher is fascinated. After several years, the teacher said, you can go back. He kowtowed and thanked the teacher and went down the hill.

Mr. Nan Guo returned to his original palace. On this day, King Qi Xuan asked everyone to play for him one by one, and it was Mr. Nanguo's turn. As soon as he finished playing, everyone applauded and said that Mr. Nan Guo played very well, so King Qi Xuan gave him high treatment and made him a musician in the palace.