Not all Arabs are Muslim, and not all Muslims are Arab. The two are not one in the same. Also keep in mind that there was no Islam in the 6th and 7th centuries BCE after the northern tribes were exiled, and the transplants placed in Samaria.
Islamic State militants blow up ancient Arch of Triumph in Palmyra (Reuters)
from the article: Ancient Samaritan sect marks Passover sacrifice near Nablus