Tink, fairly certain I have brought this up to you before...so asking now for a reprise, your current thinking?
You mention Hitler's quick victories early on ... went to his head... and some of those victories truly quite miraculous...do you think Hitler may have believed that he was doing God's work, and thus could not be stopped, with God on his side? He could then take improbable chances, ignore expert counsel from his generals...
It's not an uncommon thought pattern, to justify war thus...I can recall in the 1990's, people doing that with the Iraq war.
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At one point in the last few years, I was collecting what (I felt) might have been 'turning points;' watershed events without which the Allies could have lost WWII. One of those, of course, the work of Alan Turing and associates, their Enigma cryptanalysis at Blenheim; another might be FDR's decision to go all out in sending aid to Britain, rather than save some for home in case Hitler invaded the USA...maybe also, the French Resistance in blowing up the train tracks carrying crack Nazi divisions toward the D-Day invasion, giving Allies the time to establish a foothold...there were others, and quite fascinating, I thought!
Anyway, one point on my list was Hitler himself; made such unnecessary mistakes, perhaps in his delusion of cannot-fail-cuz-God-is-with-me...what would you say, only your educated guess, of course?