Matthew M. answered 10/24/19
Matt. M - English Teacher, Author, Illustrator, Business Owner
At the time Mexico was only just discovered and the area was rumored to have contained great wealth. Given his previous exploits and the fact that he sought this opportunity, as opposed to being sent in the name of the governor, it is likely he was seeking riches and fame.
Although Fame and Wealth are powerful motivators, they aren't the only forces at play when you look at early explorers. It takes a certain type of character and mindset to set sail into the unknown. Just as in todays world, many people are moved simply by an inner drive. The goal is simple to push themselves into unknown emotional, mental, and physical terrain.
Alternatively it may have been that he already had designs on finding a straight from the Atlantic to the Pacific, which is something that he explored in his later years. It could be that on his voyage in 1518 this was derailed due to the turmoil with the native populations and the issues with Spain.