Germany was looked upon favorably during the years shadowing the Treaty of Versailles. They were weak and in a state of oppression and as long as they allowed themselves to be plundered, they were "accepted into the fold".
But 14 years of unemployment, starvation, and homelessness triggered a desire to rise above the status of "whipping boy". The Zionist corrupt Weimar Republic ended when Hitler passed the Enabling Act. There's been a lot of controversial debate on what effect this had on the Jews, but there is no question that the very day the Enabling Act was passed, the Zionists declared war on Germany. This must have had some kind of profound effect on the Jews for them to declare war.
Britain had been a strong Zionist supporter, as evidenced by the 1917 Balfour Declaration and their support to establish a Jewish homeland in Palestine in spite of a previous agreement made with the Arabs in 1915, which they reneged on. When the Zionists declared war on Germany, Britain wasted little time throwing in their support. In the United States, Roosevelt also threw his support to the Jews.
"Zionism" - "God's chosen political group" - had to succeed at any cost.