What resistance there was to Nazism was often led by Christians. Many Catholic priests who resisted the Nazis were sent to the camps. Within the Lutheran Church, Martin Niemoller, Karl Barth, Dietrich Bonhoeffer and others led the Confessing Church. Many of them were also sent to camps. Bonhoeffer was executed.
Still, it must be understood that the Nazi regime was a totalitarian dictatorship that ruthlessly controlled the churches along with every other aspect of German society.
But what Hitler "actually" believed is irrelevant (I doubt that the notoriously debauched members of the Saudi royal family believe in puritanical Wahhabi Islam, but that doesn't make Saudi Arabia any less Islamist), what matters to this discussion is his regime's policy towards religion.
The Nazis came to power to a large part because they promised to protect Germany from Communism. This meant protecting banks and businesses from collectivization, and protecting Churches from outright abolition. While Nazi economic policy may have seemed too intrusive (especially during wartime) to business elites, they did not nationalize industries or banks.
Similarly, the Nazis couldn't very well go about shutting down Churches while claiming to be defending them from atheistic Communism. What the Nazis did instead is co-opt both the Lutheran and Catholic Churches in Germany so that their clerics would follow the party line, as well as censoring and bowdlerizing the parts of scripture that contradicted Nazi doctrine (i.e. most of the Old Testament, the Gospel of Matthew in particular in the New Testament - as the first Gospel is most explicit about Christ's Jewishness, and promoting the celebration of pagan Yuletide alongside Christmas as one and the same). As with the business elites, it was a co-option that the mainline clergy didn't appreciate but could often live with when Communism was seen as the alternative.