John is beloved because he is a disciple who himself loves much - so much that he alone of the Apostles follows Christ all the way to Calvary and stands with the Blessed Mother and Mary Magdalene at the foot of the Cross. He is our model in loving discipleship.
7th Day of Christmas: What Exactly is The Christmas Season?
There are some people who don't see the point of all this complexity: why not just celebrate Christmas and be done with it? But the Liturgical Calendar is not just about commemorating past events: it's about experiencing the events of Salvation History in our own lives.