A strange disease kills off some of the richest and most influential people on the planet. First it was the billionaires, then the multi-millionaires and so on progressively... Then it threatens to strike anyone with any sort of fortune. With the whole world panicking, people try to flood the market with assets the world no longer wants.
Columbus' 4th voyage has been a total failure: he has not found the westward passage, he has no gold to show, he has lost men and ships and his efforts to build a colony have fallen through. The monarchs of Spain are not going to restore the rights and privileges which were taken away from Columbus after the first voyage. And Columbus will be shamed. Many of his sailors who have survived, can't face the journey home. They will choose to remain on Hispaniola or neighbouring Puerto Rico.