Alternate History - What if Constantinople had not been devastated by the 4th Crusade led by its deadly rival, Venice? Could it have then lasted longer against the surge of Islam?
Sadly, no. It was on borrowed time since Manzikert
To expand.
The Roman Empire (That’s the proper name - the term “Byzantine empire” was coined by 18th century western europeans to disparage the east) lost its economic based in the ARab invasions of the 600s.
What is interesting is that the parts of the Roman world lost to the Arabs were Afro-Asiatic in language (meaning speaking either Semitic languages like Aramaic or Babylonian or were speaking Egyptian or Berber - remember that St. Augustine was a BErber)
The Greek speaking Romans alienated these peoples and the Christians of that region actually supported the ARab invasions. That’s because initially the “Arab religion” was a Christian heresy before they made up the idea of a separate “Arab prophet”
Anyway, so they lost their economic base which was Egypt and Syria.
anatolia was rich as well, but with 60% of your economy gone, you have to fight a rearguard war.
Then Anatolia was lost to the Turkic peoples and Constantinople remained a city lost from its hinterland.
The 4th “crusade” hastened the fall, but it woudl have fallen by 1500 unless Western Europeans got their act together (which didn’t happen as they themselves got divided through the reformatting)