A purpose essential to God Himself. A purpose essential to each and every soul itself. Sent to teach unconditional love. Thus Christianity and other religions have the same purpose, the same basic beliefs, the same goals. They just use different peripherals to get there.
Religions are compatible.
They can be tolerant to each other without committing self destruction. They may and should retain their uniqueness in order to provide the multitude of unique homes for the vast number of unique souls. Religions are resting places, homes, for the weary traveler, the soul itself.