Answer: They believe that Axum lost control of the Red Sea and coastal areas to the growing Islamic Empire.
Step-by-step explanation:
The Kingdom of Aksum, located in the Horn of Africa, was said to be so powerful by the Muslims that it was on par with China, the Byzantine empire and the expanding Islamic state.
As Islam spread however, the Kingdom of Aksum declined even though this was not initially the case. Aksum and the Muslims were once on good terms until relationships gradually became so bad that the Muslims took over the trade routes in the Red sea as well as coastal areas that once belonged to the kingdom.
This caused the Kingdom to flee inland for safety where they continued their decline till their demise.