In the Davidic Kingdom, the queen was not the king's wife but his mother, a powerful and official position second only to the king himself, holding real authority and often depicted as having her own throne and crown. This institution, which began with King Solomon and Bathsheba, gave the queen mother immense influence as a chief counselor and intercessor for the king. The significance of this role in the Old Testament is used in Christian theology to understand Mary's position as the Queen Mother of the New Davidic Kingdom established by her son, Jesus, the last Davidic king.
Mary was the mother of the last Davidic king. Her status is proclaimed in the Annunciation, where Gabriel tells her she will be the mother of a royal son who would restore the Davidic kingdom. This is why Mary is referred to as the "Queen of Heaven" in Christian tradition, understanding it within the context of her royal office as the Queen Mother of the New Davidic Kingdom, rather than in the pagan sense.
This is not hard to grasp unless you just don't want to grasp it.