because in the Qu'ran it says that other religions can coexist with Islam:
Say [O Muhammad!]: “O disbelievers! (109.1) I do not worship that which you worship (109.2). Nor do you worship that which I worship (109.3). Nor I shall worship that which you worship (109.4). Nor do you worship that which I worship (109.5). You have your religion, and I have my religion” (109.6).
