Because it was a Muslim Empire bet on Conquest of all non-Muslim lands (especially Christian Europe), it was hostile to trade and/or exploration by Christian Kingdoms and/or principalities. Before the Ottomans, Europe used the Silk Road and the Spice Trade Routes that went through the lands that were later conquered by the Ottomans (Asia Minor) who then blocked all trade and exploration ventures into Asia and/or the Middle East.
This forced European powers to seek alternate routes for commerce and exploration in Asia. The Portuguese were the first, they circumnavigated and explored the African coastline all the way to the southernmost part of Africa and finally made it to India. This allowed them to renew and control the lucrative Spice Trade and further map the unknown world. Spain was engaged in a hegemonic strife with Portugal and thanks to Christopher Columbus, who was seeking an alternate; shorter route to India sailed through the Atlantic and discovered the New World.
