After the cord between the Western and Eastern Empire was snapped, Byzantium would experience a harrowing contraction, especially after the plague and the mini ice age, and then resources like the Egyptian bread basket were lost to the Arab invasions. The Eastern Empire would retreat into its shell in the formidable fortified Constantinople, nursing its wounds and conserving its energy, before expanding once again when conditions improved.
But that isolation contributed to an increasing divergence of its character from the West's. Though both Christian empires, Byzantium's centralized isolation and austerity - and their exposure to the might of the iconoclastic Islamic armies - would contribute to an inward-looking and icon-refusing Eastern Christianity, which appeared increasingly alien to the iconophile West, who was developing in a more distributed manner as a network of warring Gothic states.
And this cultural divergence would further widen in time, contributing to the targeting of Byzantium in the Crusades. The twin pressures of the Crusades from the West and the successive Arab and then Ottoman invasions in the East, would close like pinchers around the shell of Constantinople, eventually cracking it like a walnut, with the Ottomans dealing the final blow.
The West had transformed in its own provincial way, and the East, holding out as long as it could, still thinking of itself as "Roman," but still developing its own idiosyncratic character, would finally wink out for good.
