What were the major motives for converting to islam when the umma opened up to non-muslims in the abbasid era?

- The status of non-Muslims was inferior. During the Umayyad Period it was specially the case, as Islam was Arab-centric and only  Muslim Arabs had access to high positions in the administration and bureaucracy. During the Abbasid Period, Caliphs decided to rely more and more on non-Arabs, notably Persians and in 930 CE a law was passed that made it mandatory for all bureaucrats of the Empire to be Muslims. Therefore non-Muslims had a professional incentive to further their career.

- The dhimmi status involved the payment of a "protection" tax that had to be paid by non-Muslims to Muslims. Poor people had no choice but to convert if they could not afford the payment of such tax.

- As the Empire prospered and developed many Muslims migrated to conquered lands that were majoritarily non-Muslim before their arrival. Their increased influx made the new majority relevant and non-Muslims preferred to convert in order to assimilate to their new reality.

the cost of college has risen faster than inflation for many years.

the high price of student services and administration are two reasons for the rapid increase in cost.