Why did the pope support William the conqueror's campaign?

Pope Alexander II supported William the Conqueror's campaign to invade England in 1066 primarily because he sought to strengthen the Church's influence and authority in the region. By endorsing William, the pope aimed to legitimize his claim to the English throne, viewing it as a way to promote the spread of Christianity and align England more closely with papal interests. Additionally, the pope hoped that a successful conquest would help reform the English church and curb any local dissent against papal authority.