They knew the earth wasn’t flat; they didn’t know how large it was.
Columbus vastly underestimated the distance or he just wanted to be sponsored to sail over.
He went a bit nuts in the new world, and was returned to Spain by knights sent to check out the situation.
They wanted to find a route to Asia which didn’t require having the Arabs as middlemen.
Eventually they got what they had wanted; a sea route from the Philippines to Mexico (New Spain), which galleons sailed for years.
Sometimes pirates attacked the Spanish galleons off Baja California Sur. An English pirate Miles Cavendish was one, think of him next time you look at the arches at Cabo San Lucas.
The phone book there had some English surnames, from pirates who decided to stay. A Mexican friend of mine from there has an English descendant and surname.
Lets not forget how we all got here.
http://www.youtube.com/watch?v=kuvRFZ4Mxbo&feature=fvw