Answer: Because certain forces emerged in different countries that forced them to do so.
I know to what extent people in Russia and other former Soviet bloc countries in Eastern Europe countries looked for every opportunity to exit. On the other hand, there were many who did not want to leave.
Even right before WWII there were Jews who did not want to leave Germany although Hitler allowed them to do so. He founded special schools for Jews in which they could learn different professions in the field of agriculture so that they could go to Palestine. These facts are based on historical documents which cannot be denied. At first there was a direct connection between the Zionists and the fascists because they wanted the same thing, the transfer of the Jews to Palestine.
On the one hand, Germany wanted to get rid of the Jews and also to gain control in Palestine to counter the British. On the other hand, this played into the hands of the Zionists and they acted accordingly. This is the reason that the Germans were ready to pay the Jews to leave Germany.
But when Hitler saw that it was useless and that they didn’t want to leave, he began the annihilation process.
From the Webinar 5/8/16