Hitler was about greed and revenge. The crusades, particularly the children's crusade, were about humans being vindictive to the point of insanity. Justinian Marched to show strength while bringing the plague was a demonstration of greed and stupidity.
Without the Crusades, we would be living in a Caliphate. It united the forever warring Christian sects. This aside.
Really? The first crusade utterly wrecked the economy of the Byzantine empire, the buffer against Islam. They never really recovered. The crusader states were inherently unstable. But what's interesting is the Muslim reaction to the crusader states, ie none. Saladin conquered the crusader states while on the way to somewhere else. The crusader states didn't even act to unite the Muslims against them. They hardly gave a shit. Saladin acted on his own.
The Ottoman Caliphate was cosmopolitan. They had no interest in converting anybody to Islam. Until quite late they even forbade conversion.
The Islamic world only started getting upset about the Crusades in the modern anti-colonial rhetoric. Then they backdated the grand narrative of the Islamic conquest and the importance of Saladin.
What protected the west from the rule under the Caliphate was Vienna in 1520'ies. It was about military technology. Not religion
I think you're repeating a modern myth that was never true.
