Let's assume that ITTL Germany and Italy fight WWI together, yet lose to the Entente nonetheless. Convergent butterflies make it so that a WWII still happens in the late 1930s, yet they have sane far-right leaderships that leave the Jews alone. Hence, all the Jewish German-Austrian, Italian, and Hungarian scientists that IOTL fled to the Allied countries stay home, except for the dedicated antifascist militants. Moreover, since Germany and Italy ITTL are oldtime allies that trust each other as much as the western democracies did IOTL and planned rearmament together, they start a joint atomic research project soon after the beginning of the war. How quickly would such an Axis "Project Vulcan" build the Bomb ? And how well would the American and British projects fare without the expatriate European scientists, or the Soviets without being able to spy on the same ?