Hey Sir Adrian,
I don't have any particular problem with any of your point, but I would like to elaborate on your third point. One of the factors for the Renaissance was the enormous wealth generated by the Italian City states that traded through the eastern Mediterranean. They obviously benefited from the Crusades, which opened the trade routes, but it was the wealth that allowed them patronage the artist and building projects that allowed the Renaissance to get started.
For your point, the "Europe" certainly had a interest in ensuring the survival Byzantine- it was an ideal buffer to Arabic expansion.
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