Not only they spread christianity they also have to keep the ark of covenant in a special church and they guard (I have relatives in axum and have shown me pictures of it!).
It grew mostly because of its trade with the ancient Romans and with India; at the height of its power, the empire was strong enough to create its own money.
converting to Christianity
the foreign merchants brang new idea's and beliefs,along with trade goods.
According to some Islamic traditions, the people of Axum offered shelter to the family of the Muslim prophet Muhammad during his exile from Mecca from 622 to 630 CE. For this reason, Axum was left untouched while Muslim armies conquered the surrounding areas.
Coins.
When Muslim Arabs took control of the Red Sea and Indian Ocean trade, they limited Aksum trading.
Aksum is the name of a powerful, urban Iron Age Kingdom in Ethiopia, that flourished in the centuries before and after the time of Christ. Its location made it prosper because the surrounding nations were so underdeveloped.
Ge'ez (ግዕዝ) was spoken in the ancient Kingdom of Aksum, which is now present-day Eritrea and Ethiopia.
Textiles (apex)
It is true that Kush was invaded by Rome,