Why is that?
According to a curious article on the website of the Arabic-language Egyptian newspaper, Egypt Independent, which was founded in 2011 and headquartered in Cairo, ISIS claims that their god Allah commands them not to fight Israel or Jews. Instead, ISIS's immediate enemies and targets should be apostates — a word that variously means turncoat, heretic, atheist, or infidel. The article then makes a historical reference to how Saladin (1137-1193), the Sunni Muslim military commander, had fought Shiite Muslims first before capturing Jerusalem. The implication is that ISIS should focus on fighting fellow Muslims who are "apostates," and conquering countries like Iraq and Syria.