Why do Christians keep insisting that Hitler was an atheist, given that he often invoked God in his speeches?

His book Mein Khamp repeatedly mentions God and Jesus in a positive light, he lived and died a Roman Catholic in good standing (he was never excomunicated!!!), he asked his close lieutenants to remain loyal Catholics, his SS officers had "God with us" on their belt buckles, Germany was a Christian nation and would never have accepted a atheist leader, his spokesmen said things like "Hitler's word is God's law", etc, etc...