That supposition is mostly false. The idea that the popes were in league with the Nazis all the way is damn lie. IF you lookat Nazi thought and ideology(especially that of Heinrich Himmler and Reinhart) They believed in a "superman" concept, which is NOT compatible with any kind of Christian teachings. They also had many Germanic pagan symbols on their suits, party flags, and other things.(Example: The SS symbol looks VERY similar to Germanic Runes) The alliance with the Vatican was only temporary. In fact, if you look hard enough, you'll find that the Nazi gov't of Germany had NO PROBLEM AT ALL with going ahead and expelling Christian pastors, preachers, Reverends, Bishops, Deacons and priests from Germany.
Hitler said in private:
You can't make an Aryan out of Jesus, that's nonsense."
"It if weren't for Christianity, we wouldn't have Islam."
Goebbels and especially Himmler hated Christianity deeply, and they along with most of the inner circle of the Nazi party, wanted to ultimately remove Christianity from Europe.
Hitler also said something along the lines of: "Christianity, when taken to its logical extreme, results in the ultimate cultivation of the Human failure.
"I shall crush Christianity under my boot like a poisonous toad!"- Hitler again