Why did Buddha want to become the "enlightened" one?

He was the one who founded the religion of Buddhism (He was a prince). One day he saw an old man, he had never seen such thing in his entire life. Then he went to that city again and he saw people carrying a coffin. inside was a dead man wrapped. in those two moments he learned about death and old age. He learned of other miserable things too. He became really sad and depressed. then one day he found a saint meditating, there he learned that you need to seek for truth. So, he took a Journey and discovered that there is no way to get out of this suffering and then under the tree of enlightenment, he became the enlightened one