Why are Christians viewed as infidels in Islam, even though the Prophet permitted marriage to a Christian woman and allowed her to remain in her religion? Does this not indicate that she is not an infidel?

We Muslims believe that Allah is One and Unique, and in all the prophets and messengers, making no distinction between any of them. For whoever disbelieves in one messenger has disbelieved in all messengers and in Allah, as Allah the Almighty says: "Indeed, those who disbelieve in Allah and His messengers and wish to differentiate between Allah and His messengers and say, 'We believe in some and disbelieve in others,' and wish to adopt a way in between - those are the disbelievers, truly. And We have prepared for the disbelievers a humiliating punishment." We believe that Jesus is the servant of Allah and His messenger, and that whoever bears witness to that shall enter Paradise. We believe that Jesus is not God, nor the son of God, nor one of a trinity, and whoever believes that is a disbeliever. As for the permissibility of marrying women from the People of the Book, it is restricted to those who are chaste and not fornicators.