Why do you think Cabeza de vace wrote of great riches that could be found in the Americas

Cabeza de vaca wrote about the great riches in the America because he wanted the future explorers to discover the riches. Also he he might wanted to let the country he travel for know about it before he die, so the country can sent explorer to discover it before other country do.

To either encourage the idea of a spherical world, or he just wanted to make money.