Byzantium was still a magical place in Napoleon’s time. I understand he proposed to make the City the capital of his world empire.
He invaded Russia because they would not stop trading with the British.
At this point in time Napoleon was arrogant to the Nth degree.
If he had instead allied with the Russians in a joint invasion of the Ottoman empire if the Russians cut off trade with England he would not have lost his army and empire at the gates of Moscow.
Of course neither France nor England wanted Russia to have a warm water port and because of this the French and British a generation after Napoleon allied with the Turks to fight the Russians in Crimea.
The Turkish empire was preserved by the so called Christian nations of the West because it boxed in Russia.
So much for Christian unity....