Beginning at the end of 1941 Nazis set up six mass killing centers in Poland -- Auschwitz, Treblinka, Sobibor, Belzec, Chelmno & Majdanek -- in which about half of all murdered Jews died.
The rest died in other camps -- so called "work camps" -- in Einsatzgruppen shootings and from starvation & disease in restricted ghettos.
None of this was going on before September 1939.
Yes, during the 1930s Jews were harassed, restricted & persecuted, but they were not being mass-murdered in the way that only began after two years of European war.
This is the immediate context for your not being mass-murdered world for the the Jewish refugees on the St. Louis and occurred just previously in November 1938. The Jewish refugees were able to arrange for passage and fled in May 1939.