In 1492 some Portuguese commissioned vessels managed after many weeks to cross the relatively narrow passage from Africa to the Carribean. A bit later Cabot from Britain managed to cross the Northern route and land on Continental America.
Both trips were fraught with danger and at the extreme edge of technology and navigation skills.
The somehow 60 odd years later the Spanish were navigating across the Atlantic and Pacific with ease and conquering the Phillipines and most of West Coast North America in the process.
How is this possible? Was there some instant revolution in ship building and navigation? Or some other factor at play?
I can’t imagine that the later voyages were much less hazardous than the first. It may seem that way because of (a) the greater number of vessels making the crossing, once the possibility of it was established; (b) the infrastructure that was set up on both sides of the Atlantic, which would have facilitated such journeys; and (c) the experience gained in navigating and charting previously unknown waters, like the Caribbean.
The wealth looted from Central and South America no doubt funded a vast expansion of the Spanish fleet and provided an incentive for multiple voyages.
A lot of it was just learning the typical wind and current patterns, as well as where islands and other land masses were. For example, when Magellan crossed the Pacific he did it more or less diagonally. It took him three months and he lost a number of men to scurvy. Later the regular route that was established across the Pacific ran from Acapulco to Manila, which was much shorter.
Note that in both the Atlantic and Pacific the eastward and westward routes were quite different. This was in order to take advantage of the prevailing winds in different regions. It took some time to find and learn these routes.
By the time Columbus et al were crossing the Atlantic, the Portuguese were already sailing around Africa, a much longer distance. So the ships were quite capable of the journey. from Columbus’ experience, the biggest “fraught” was not knowing how far they were going and how much supplies would be needed. (The trans-African ships I guess would stop every so often to fill up with that healthy African river water?)
So the previous posters have it better - the major problem was the unknown.
There was a “revolution” in navigation in the sense that people figured out where to go to catch the right currents and winds. It’s not just a case of pointing your boat toward the landmass you want.
When Vasco de Gama sailed to India he didn’t just hug the coast of Africa. He couldn’t, in fact, since there are strong northerly winds running up the western coastline. Instead he had to sail out almost into the middle of the Atlantic to catch currents that shot him back east towards the Cape of Good Hope. This may explain why he was such a shithead to the people he found on the other side of Africa.
One thing which was happening in this period is that naval power became much more important, and consequently a major focus for some governments. Not that many of these governments had no naval power before the 1500’s, but it during this era that they began building a strong core of professional naval power. Additionally, the constant trade across the Atlantic, combined with that development, led to long-term improvements of ship design. They grew larger, taller, faster, better able to ride storms - and much more heavily armed.
However, the basic technologies were all right there in the carracks that carried Columbus to the Caribbean. Transatlantic ships would largely take that form until the development of ironclads, and soon after all-metal vessels.
There are a lot of things where once a target or objective is achieved, others soon follow. After Rodger bannister ran his four minute mile, which had been thought impossible for decades, it wasn’t long before others reached the same target. “Within a year after he did it, so did 24 others.” - not true, but there were at least four within two years.
Plus, the Spanish and especially the Portuguese were sailing the Atlantic, where from what I recall, the seas could be a lot wilder than the Mediterranean where it was hard to get far from shore. The Venetians, for example, who sailed the eastern med with a large trading empire, tended to have galley ships. (The Arsenal IIRC was an assembly line for these) That sort of tech did not scale up to Atlantic use. It fell to the Iberians, and the North Sea denizens, to develop real ocean-going vessels.