"Jewish scientists form the largest single religious or ethnic group of Nobel Prize winners from the United States." Why/when/what?

There was an "intellectual" migration in the 1930's from Germany to the United States due to FASCIST oppression in eastern Europe. 1150 Jewish scientists migrated from Nazi Germany.

Had Hitler never been born those scientists would likely have remained in Germany leaving the United States high and dry?

We will never know will we?