seljuk

For starters the caliphate was only a political force until the emergence of the seljuk turks.

True, but Nasreddin was not from Persia but from Asia Minor during Seljuk rule.

The Eastern Roman Empire fell in 1453 when the Seljuk Turks conquered Constantinople.

It was the expansion of the Seljuk Turks that brought Turkish-speakers into Anatolia, and they became the dominant people over the next few centuries.

Did the Seljuk Turks betray the Byzantines when they conquered Anatolia?

The Ottomans start as one of the beyliks in the ruins of the Sultanate of Rum, which is Seljuk (Turkic) Anatolia wrested from the Byzantines.

Even for Seljuk Turkish state it was a little too early.

The Seljuk Turks moved into central Anatolia (this is what prompted the Crusades), and did seek to take Constantinople, although they were done in by the Mongols instead.

The Muslim Seljuk empire grew from Nomadic tribes, but didn't really threaten Europe.[2] The Umayyad Caliphate was a well organised, centralised empire by the time they invaded Spain.

> Did the Seljuk Turks betray the Byzantines when they conquered Anatolia?

It was in response to the rise of the seljuk Turks and their advance on the Byzantines and also similar to the Muslim invasions of the middle east, northern africa, southern italy, and spain.

Or maybe the tyrannical nature of Christian rule had weakened its victims until they could no longer suppress learning and innovation — nor resist conquest by more highly developed cultures, as in al-Andalus, the Seljuk Empire, and eventually even Constantinople itself.

The Seljuk-Crusader War wasn't a real war?

With 20–40 minutes of effort, someone could easily track down a large pile of peer-reviewed scholarly literature examining the contributions of Arab, Persian, Seljuk, etc.