Well it is only rational if you accept the science they used to come to their conclusions in terms of hilter's personal ideology. That said the way the nazi party went about it was monstrous.
If you are talking about tactics... if he simply bribed the soviets and dealt with the allies before turning on them I doubt he would of been stopped from uniting all of Europe.
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Pretty close to it... that isn't to say they did so through some massive strategic victory. They simply had massive amounts of fresh troops to deploy on a tired and wounded enemy.