Jews Served and Worshiped the Devil
This theory was developed and preached (still is, unfortunately) by some fiercely anti-Semitic Christian theologians. According to them, modern Judaism (more correctly, Rabbinic Judaism) is not the religion of the Old Testament (and thus has nothing to do with Christianity at all), but is an entirely new religion. Religion of the Devil.
These Christian theologians believe that by rejecting Jesus Christ, the Jews automatically rejected God the Father (God of the Old Testament that is) as there is no way to the Father except through Jesus Christ.
Consequently, while the Jews pretend (or maybe even believe) that they worship God of the Old Testament, in reality they are worshipping entirely different entity. Who is NOT the God of the Old Testament and, therefore, can only be the Devil.
Who for two millennia was carefully making out of the Jews a very powerful spiritual weapon to be used for conquering our world, destroying the global human civilization as we know it and replacing it with a Satanic “alternative civilization” (“anti-civilization”).
By mid-XIX century the Devil achieved the “critical mass” of the Jews which allowed him to develop the ideology (quasi-religion, actually) of Marxism which later was transformed into an even more powerful spiritual weapon – Bolshevism.
Then the Prince of Darkness used a relatively small number of Jews to create a physical weapon – the Bolshevist party and the Bolshevist state – Soviet Russia (later transformed into the Soviet Union). Which launched an existential war against the whole human civilization (including its Christian component) to achieve the abovementioned objectives.
To win this existential war, the Nazis (who were the only power capable of stopping the Bolsheviks and thus saving the human civilization) had to destroy a significant part of Jewish spiritual infrastructure in Europe and physically exterminate millions of Jews (to weaken the “Jewish egregor” and thus the Bolshevism and ultimately the Devil).
While at first glance this theory seems plausible, in reality it is not. First, the Jewish Bolshevist leaders in Russia, Germany, Hungary, etc. were atheists and thus had no connection to Judaism.
In fact, from the very beginning the Soviet leaders (including the Jewish ones) persecuted wealthy and religious Jews, destroyed synagogues, etc. In 1919 the Soviet authorities abolished Jewish community councils, which were traditionally responsible for maintaining synagogues. They even created a special Jewish section of the party, whose tasks included propaganda against Jewish clergy and religion.
The training of rabbis in the Soviet Union became impossible until early 1940’s, and until the late 1980s only one Yiddish periodical was published. Because of its identification with Zionism, Hebrew was taught only in schools for diplomats.
Most of the 5,000 synagogues functioning prior to the Bolshevik Revolution were closed under Stalin, and others were closed under Khrushchev. Consequently, the Jewish Bolsheviks were enemies of Judaism and thus the highly unlikely tools of the latter.
Second, although the overwhelming majority of the Jews did reject Jesus Christ as their Lord and Savior, it is still highly unlikely that the loving God would have had completely abandoned his chosen people to his sworn enemy. Therefore, it is completely inconceivable that the Jews believe that they worship God of the Old Testament but in reality worship the Devil.