We are going back to the period of Constantinople invasion. Crusaders came to Constantinople and they invaded Constantinople instead of lasting the campaign. Crusaders ruined the capital of East Roman Empire and created a big destruction. Some Greeks could run away from Constantinople. They came to Trebizond that was another Greek colony in Small Asia. Finally they established Empire of Trebizond in 1204. Their purpose was to get Constantinople back sooner. This was the fact that it would take time to achieve this goal. They dominated the Black sea region and Crimean shores. They built family affairs by marriages. Ex- Byzantines built their own St.Sophia in Trebizond but it was smaller than the one in Constantinople.
Bithynians got Constantinople back in 1264 and some royal family members came back to Constantinople. Empire of Trebizond had lasted till 1461.
It is a great resurrection story in history.