Hernan Cortes went against the wishes of his superiors to gain a better position for himself.
At the time and shortly after the discovery of the Ne World, there were a lot of opportunities to gain wealth and power. The richness of a whole continent was available, and the natives could not secure it for themselves. Additionally, the situation was slighlty chaotic, which contributed to the fact that frauds could escape undedected.
One of the times when Cortes was working against his superior (Velazquez) was when he led an expedition to Yucatan, althougth Velazquez revoked his original permission to do so.
