A: Once France fell in summer of 1940, and specifically Paris fell, refugees started streaming to the south of France. As Germany consolidated its control, they moved into Spain and Portugal to try to get out of Europe to get to America or somewhere else in the free world.
Many of these refugees were Jewish, and they were desperate to escape the horrors of the Nazis. As Arthur Koestler said [in a 1941 book], "Lisbon was the bottleneck of Europe." It was the last chance to get out.
[Koestler, a journalist, added that Lisbon was "the last open gate of a concentration camp extending over the greater part of the Continent's surface."]