Answer the following question!

    Once upon a time, a village suffered from drought, so the people could not cultivate the land. Nusa's family decided to move to another place to find fertile land. They arrived at fertile land and started to cultivate it.

    One day, Nusa found a big egg and asked his wife to cook it. He ate it, but his wife and brother refused to eat it. They wondered what egg was it. In the morning, Nusa screamed because his body was full of scales. Then, he changed into a dragon. He asked his wife and brother to move him to the river.

    Later, the dragon became a predator in the river. He ate fish there which made the fish scared. The fish held a meeting to solve the problem. Then, they had an idea to trick it. The fish swam to Nusa and said, "Master, look at behind you. There is a dragon who will attack you." The dragon turned the big body very fast with his tail still in front of it. The dragon thought its tail was its enemy. The dragon bit the tail and it dies.

    Finally, its body slowly changed into an island and people named it Nusa Island.

(Translated from: http://dongengceritarakyat.com/cerita-rakyat-kalteng-asal-usul-pulau-nusa/ (September 25, 2019))

Why did Nusa change into a dragon?