So this is a question that I asked in r/History a while ago. From how I understood it, after the fall of Constantinople to the Turks in 1453 they banned Europe from the trade with the East, which drove the western kingdoms to seek alternative routes to the Indies. My question was why would they do that, given how controlling the spice and silk trades would be incredibly profitable for the Ottomans.
The reception wasn't overly friendly, and they made quite sure that I understood that I was wrong in my belief that the Turks had prohibited Europe from trading with East Asia. But they forgot to mention exactly what the Turks had done that forced Europe to look for alternative routes to the Indies.
So my question is that: What exactly caused the Europeans to seek other routes to the Indies after the conquest of Constantinople in 1453?
Any help is greatly appreciated.
I've written about it few times before, and basically your hunch is right, the Ottomans never stopped the trade, nor was Constantinople that important for spices in the first place, nor does the fall even matter as the Portuguese started going down Africa even before 1453.
To put it simply, the Iberians just wanted to get to the source of spices and buy them cheap and sell expensive in Europe, Ottoman actions don't really matter in this decision process.
My previous answers