Without centuries of Christian antisemitism, Hitler’s passionate hatred would never have been so fervently echoed. Robert Runcie, Archbishop of Canterbury
Nazi anti-Judaism was the work of godless, anti-Christian criminals. But it would not have been possible without the almost two thousand years’ pre-history of ‘Christian’ anti-Judaism…” Hans Küng
Attributing Hitler’s actions to his Christian belief’s is a common argument heard in anti-religion/anti-christian circles. At the same time, claiming that Hitler was an atheist/Darwinist and that his actions were a direct result of his lack of belief is used widely by Christian apologists to prove how dangerous atheism/Darwinism is.
Both these views, and let me say this without mincing of words, are ill-informed, unscientific and to a large extent dishonest. Nicely said, they don’t examine the issue sufficiently before drawing conclusions, and therefore reflect more on inherent biases than facts.
Hitler was likely a psychopath or someone with an anti-social personality disorder.[ 1]. His ideologies and beliefs varied over time and were an amalgamation of many, often conflicting, ideologies. He had no single religion, did not believe in conventions of morality and showed no signs of remorse. He was as close to a monster a human being can become. He used whatever tool, ideology, politics and misinformation he could to manipulate people into buying his murderous intents[2, 3]. He was also, later in his life a drug addict, with expected effects on his brain.
Anyone who is familiar with methods in historical research will know that historical figures attract rumors, fables and myths like honey does ants. Research is further confounded by the fact that most of the people close to Hitler were inveterate liars, and had absolutely no moral compass so would not hesitate to make up stories and pass them off as the truth.
In spite of all this, I believe that a fairly accurate picture of Hitler’s motivations is emerging. To begin with, I think it is sufficiency clear that he was raised a catholic and his up bringing had some influence in his views about Jews. Jews were second class citizens in Germany and the leader of the protestant reformation in Germany, Martin Luther was an avowed Anti-Semite. Christianity has a long history of persecuting Jews, from as early as the time of the church fathers, many of whom including Justin Martyr and Augustine espoused the “Jews are Jesus killers” ideology. But it is also clear that as Hitler’s antisemitism grew stronger, his faith in anything else grew weaker. By the time he was the Fuhrer, he was not a devout anything, except Nazi. He was a megalomaniac and considered no one, natural or supernatural to be better, greater or smarter than himself. But he used religion very effectively to promote his ideas. He used the passivity and opportunism of the Christian churches, as well as the underlying antisemitism very effectively to come to power and take total control of the state .
History: How Events unfolded
Till the First world war, protestants were the dominant political force in Germany, however after the war, the catholic church and the “Center Party” that was formed by the church were increasing in power. This alarmed protestants very much as they saw the “danger of Rome” looming and before the days of his ascension to Chancellor, protestants were very much in love with Hitler, as he was seen as the only opposition to the power of Rome as well as the evil of communism, as the catholic church had started to flirt with socialism.,  Hitler became chancellor in January 1933, with blessings from the centre party and 15 days later, Pope Pius XI, signed a Concordat (Treaty) with the German Reich 
According to the concordat, the catholic church was given recognition to function independently, but also that the bishops and clergy would function in accordance with the rules of the Reich.  But very soon after Hitler took on power and became a dictator, both the catholic and the protestant Churches realized that he was least interested in allowing them to continue in their positions of power. Through a series of smart moves, Hitler successfully dethroned both the protestant theologians and the catholic clergy from the position of power and installed his own men and spread a very convoluted Nazi Christianity.
Hitler’s only aim was to take total control, and after he had wooed the churches into placing him into this position of power, he placed his hand-picked people in charge of churches, who preached a Nazi or Aryan supremacist version of the Bible. Needless to say, while this movement picked up a lot of momentum and was very powerful, its teachings had little or no semblance to Christian teaching. These leaders also replaced a lot of christian rituals with Nazi rituals, slowly but powerfully abducting the church for its political and social power.
Not all of the church that took this in the stride, there was a significant minority who opposed every stop of the national socialist movement, these were the “professing Christians” as Bonhoeffer calls them. One such group was Pastors’ Emergency League founded by Martin Niemöller in 1933. This group got together in Barmen, May 29-31, 1934 and issued what is known as the Theological Declaration of Barmen. It was written by the theologian Karl Bath. The declaration was an appeal to evangelical Christians in Germany to realize the danger of Hitler’s intentions and the growth of the “German Christian” movement which had replaced the bible with the Mein Kampf and was preaching a perverted Nazi-Christ. 
In Part 2 We will look at a bit about Hitler’s Beliefs and some concluding thoughts about religion and violence
References and Further Reading
Oath required of German bishops by the Nazi-Vatican concordant - In the performance of my spiritual office and in my solicitude for the welfare and the interest of the German Reich, I will endeavor to avoid all detrimental acts which might endanger it.
Official statement by Catholic Bishops on Catholics and the new regime -
The episcopate believes it can cherish the confidence that the designated general prohibitions and warnings need no longer be considered necessary. For Catholic Christians, to whom the voice of the church is sacred, it is not necessary at the present moment, to make special admonition to be loyal to the lawful government and to fulfill conscientiously the duties of citizenship, rejecting on principle all illegal or subversive behavior.
12 The Protestant Church in Hitler’s Germany and the Barmen Declaration by Paul Kroll, You can find the full text of the declaration here