OTL Axum had a significant Jewish population, was polytheist until King Ezana in the mid 300s, and eventually conquered Himyar in the 500s (after Himyar attacked Axum). And there was a
Jewish kingdom in Ethiopia that rebelled from Axum in the early 400s (as a reaction to Ezana's conversion to Christianity).
If Himyar conquered Axum, or if Ezana became Jewish instead of Christian, or if Semien subsumed Axum ... that could have happened.
It would butterfly Islam. Muhammad was only one of multiple self-proclaimed Mashriqi prophets (e.x.
Musaylimah,
Al-Aswad Al-Ansi,
Sajah,
Saf ibn Sayyad,
Tulayha ibn Khuwaylid, 7th century;
Abu Isa,
Al-Muqanna,
Ustadh Sis, 8th century). A Jewish kingdom or network of allied realms stretching from east Africa to Persia might mean that the specific warlord-prophet figure who arises would utilize Judaism and wouldn't start his own religion. That person might be coopted by a Jewish kingdom to legitimize their rule over the others (similar to
the Biblical prophet Samuel). Or that person might unite the Jewish realms under his own, specifically Jewish, banner.
A Jewish Arabian and east-African empire (or network of allied states) within the Sassanid Persian sphere of influence, working together against the Greek Christian Roman empire ... I'd read that TL.