More than anything, the Spanish were seeking wealth.
Christopher Columbus himself thought that he had reached India: he wanted the wealth from the trade with Indians.
In the beginning, the Spanish hoped for Gold and Silver, later also for other products that could be made cheaper in the New World.
In short: the Spanish were not interested in Mexico but in what the ships could bring from Mexico (again, mostly gold).
Some, very few Spaniards, who settled in the New World were too unhappy in Europe and hoped for a better life.
The geography influenced the economic development of New York, Boston, and Charleston, because they were all ports and this helped with trade (both import and export). There were many ships coming in and coming out and also due to this, many communities started settling there and towns started booming due to the growing amount of people.
The farmers produced more food than needed and were able to feed people like the craft workers and traders
