The Makedon empire, or Basileía Rhōmaíōn as it was called at the time is one of the sucessor states of the Roman empire, that splitted from the Byzantine empire in the 700s under the macedonian general Alexandros Angelius (later known as the Alexander the great, not to confuse with the first alexander the great) and was for the most of it's existence a enemy of both the Byzantines in Constantinople, the Carolingeans (and later the HRE) in the north and italy, and the arabs who constantly raided southern greece and Italy. Let's say that there is no byzantine civil war and the Makedonian empire does not split, what could have happened? We know that it's capital, Thessaloniki, was one of the richest cities on byzantiun and it was a huge blow for the eastern romans to lose it, could this have prevented the Byzantine collapse in the levant and anatolia?