Because Columbus sailed to the New World three times and returned most people have such a pathetic understanding of history they really believe that was the only possible outcome. In fact, he was taking an extraordinary risk. He got Ferdinand and Isabella to fund the expedition by convincing them of the alternative theory in which longitudes were a lot narrower than they actually were. If the Americas had not been in the way all would have died.
There was a huge risk in taking these ships into warm waters. After not too many months an enormous mane of sea weed would adhere to the hulls substantially cutting their speed. Worms would begin boring holes in the outer planking eventually creating leaks. Ships of that era were notoriously bad sailors, and therefore made little headway into the wind. Many sailors were reluctant to sign on, because there was no assurance the ships would ever find a sustained following wind to reach Spain again.
Columbus was in a lose-lose-win type situation.
When the royals funded this first adventure...it wasn’t actually a hyped-up thing. Upon landing in the new world, he’s discovered that the ultimate purpose of this...sailing into China and creating a whole new trade route...is screwed up and he’s found a whole new place.
To ensure that they will fund the second adventure...he’s left part of the crew there, and hyped up ‘gold’. He returns, and wants a second trip financed. With the ‘gold’ angle...now he’s got lots of interest among dozens of people around the royals.
If he hadn’t done the crew-back-there trick or mentioned the gold....all of this adventure business would have ended right there.