Final answer:
Portugal likely agreed to the Treaty of Tordesillas in 1494 because it was based on limited geographical knowledge and the desire to secure eastern trade routes without realizing the full extent of the territories involved. It was a result of the competition for the spice trade and efforts to maintain peace between Spain and Portugal.
Step-by-step explanation:
The signing of the Treaty of Tordesillas in 1494 was significantly influenced by the limited knowledge of geography at the time. When the treaty was negotiated, only a few islands such as Hispaniola and not the entire continents nearby were discovered by Columbus. This geographical unawareness could have led Portugal to agree to the terms of the treaty, presuming they were securing lucrative trade routes to the East without full knowledge of the extent of the territories involved. The division created a line between the Portuguese-held Cape Verde islands and the lands discovered by Columbus, with Spain claiming the west and Portugal the east. This treaty emerged from the rivalry between Spain and Portugal to ensure monopolization and peaceful division of newfound lands and routes, following the economic and political climate influenced by the spice trade.