Why did it take a long time from the idea to the implementation of the trip to the shores of India around Africa?

The Portuguese nobility and the trading class were very interested in opening the sea route to Asia (in particular, to India and China). However, by that time, nautical charts did not exist, there were not many navigators who had experience in long voyages. And therefore, it was possible to go around Africa only 70 years after the first expeditions. The path was also complicated by strong sea currents and frequent storms; the Europeans had no idea about the seasonality of monsoon winds and the fact that they change their direction in winter and summer.