from what I know (reading, etc), a lot of German Jews were genuinely shocked and surprised to find "their" country being ripped out from under them.
according to
this article and others, about 100,000 Jews served in the German army in WW1.
Jewish chemist
Fritz Haber developed poison gas for the German army to use!
I got more info
here.
Fritz Haber converted to Catholic in his early and somehow tried his best to remove all of his Jewish ancestry, just I think the opposite of Albert Einstein. Fritz Haber invention before the war was also very important, rather more practical than Einstein relativity, with his Haber Cycle for fertilization production.
Looking at the viewpoint of German scientists, I think there still will be plenty of them that could develop A-Bomb other than Albert Einstein. Einstein basically only provided the general theoretical concept of atomic bomb but not the actual concept on how one could build it from scratch. It took a lot more scientists and engineers than Einstein in Manhattan Project. But of course Germany chance to build one would be significantly higher if Einstein would join in some German "Manhattan Project" because other Jewish scientists would probably follow suit also and FDR would not know the early possibility of it if Einstein would not send the letter of notification.
One of the most important scientist other than Einstein is Max Born, the man left Germany at 1933 once Hitler took power because he was regarded to have a Jewish Ancestry. One of his Phd students at Gottingen was Oppenheimer. He was also assisted by Enrico Fermi, Teller and Wigner. There was also Otto Hahn, the first man who split atom. All of them were important figures in atomic bomb development and later worked in the Manhattan Project.
If nearly all the world's finest atomic physicist were still in Germany, I think Germany got a pretty big chance in developing the A-Bomb before anyone else does.
The question is, what motivation would they have? All of them did not personally like to research nuclear weapons technology. Could they be convinced to create one to safeguard the world from the Communism?