Why did Isabella and Ferdinand give Columbus money to pay for his first journey?

The civilization of each historical moment has a certain level. The newer the moment, the higher the level.

The best technologies of civilization have their preferred winter temperatures. The higher the technology, the lower the preferred winter temperatures. The reason is that too low winter temperatures freeze technologies. And too high winter temperatures destroy technology by monkeys and ape-like people.

At that historical moment and for that level of civilization in Portugal and Italy, winters were too warm. And France and England had too cold winters. And at that time the best place for civilization was Spain. And this region was the best place for the development of technology and science.