There is nothing to explain my friend. Catholics are held to a belief that was promulgated in 1854 under pain of mortal sin. The Orthodox have no such doctrine…it is not necessary. There are theological opinions on the matter (just as Limbo was/is a theological opinion for the Catholic church).
The Orthodox love and veneration of the Most Holy Theotokos is profound.
Discussion?

I think it shows why this doctrine should have stayed in the realm of theologoumenon for the Latins.
There have been different opinions throughout history. Thomas Aquinas and Bernard of Clairvaux had some problems with the idea. Bonaventure was hesitant to accept it. Anselm says she was born with Original sin. The Dominicans and the Fransicans found themselves on opposite sides of the debate. I remember reading that Catherine of Sienna had a vision opposing the dogma. St Gregory Palamas believed that all generations in St Mary’s family tree were sanctified. Others believe that, at the moment when, through the power of the Holy Spirit, the divine nature was united with human nature in the womb of the Virgin Mary, the Virgin Mary first tasted her freedom from the so-called original sin and its consequences. Thus her womb became “more spacious than the heavens.” Still other great Fathers (St John Crysostom) claim that she even committed some minor sins, (what you would call venial), during her life.
To this day when I ask Roman Catholics about the IC doctrine, the vast majority think I am referring to Christ’s birth (or conception).
So you see…for the Orthodox, the 1854 doctrine is irrelevant; there is no need for it.