My take, as a German, without looking up the historic consensus:
In Germany the oppression against Jews gradually increased from 1933 until WWII started in 1939. This gave many the opportunity to emigrate.
In Eastern Europe, Germany quickly invaded („Blitzkrieg“) and immediately stated rallying the Jews into ghettos and started murdering them. There was no real chance to emigrate or flee.
My take, as a German, without looking up the historic consensus: In Germany the oppression against Jews gradually increased from 1933 until WWII started in 1939. This gave many the opportunity to emigrate. In Eastern Europe, Germany quickly invaded („Blitzkrieg“) and immediately stated rallying the Jews into ghettos and started murdering them. There was no real chance to emigrate or flee.
Edit: a typo