Why would his mother think he was out of his mind if she were without sin and knew from the beginning who he was? Why would she have shown doubt?
Further, once she shows up, Jesus doesn't show her any preference or overt favor - he doesn't run right out to greet her. No, in fact, he stays inside and says, "Who are my mother and my brothers? These are my mother and my brothers. Everyone who obeys the word of God is my mother and my brother and my sister." (I'm paraphrasing from Matthew).
Jesus does not show any preference to Mary. When she asks him about the wine at Cana he doesn't jump right up and do what she asks. In fact, it's almost a rebuke. He says, "Woman, what does this have to with us?". He ultimately agrees to help out, and performs a miracle, but he almost acts annoyed by her request. His time had not yet come.
Mary is mentioned all of six or seven times in the New Testament. Apart from the beginning of Luke, the Magnificat, there isn't a whole lot more about her. We know she was with him at various points, and among the "women" who followed him, and was in Jerusalem during the Crucifixion. But none of the New Testament writers show that she had any special role or position apart from agreeing to cooperate with God in giving birth to the Messiah. This makes her a wonderful and blessed girl, and mother, but apart from that special respect and memory, every other thing about her that the Catholic Church developed as doctrine is simply baseless.
It doesn't take any deep searching of history to quickly determine that the pagans coming into Christianity in Ephesus in the 2nd century latched on to Mary and that the cult of Mary developed out of those Christians who came out of goddess worshiping cults and were looking for a substitute.
It wasn't any kind of conspiracy or anything deliberately malevolent. In my view, and from everything I've read, it simply was an organic process that set in, and the more focus placed on Mary, the more important she became, leading to even more focus on Mary, etc. All of this set up a cycle of increasing attention paid to Mary, eventually justifying "prayers" to Mary and all the additional doctrines that came along after.
This does not remove the fact that it isn't a true part of Christianity, it's unbiblical, it takes away from the Son, it focuses worship (prayer, in my view, and the view of many others, is a form of worship) on the creature not the creator, and it's a big, unnecessary distraction in general. There is no historical basis for it. There's definitely no scriptural basis for it.
The Scriptural basis of the unity of God, the eternity of the Word and the Incarnation is actually sufficient in itself to arrive at the conclusion that Mary is the Mother of God. God gave us reason and guided by the Holy Spirit the Church comes to an ever deeper penetration of the profound depths of Divine Revelation (Jn 16:13), which being the Word of God cannot be exhausted by a bare-bones literal reading - “if it isn’t explicitly in Scripture then it is revealed.” By this logic most prophetic matters referring to Christ in the Old Testament could be dismissed because they were hidden in types and presented as shadows. Thus the simple logic of the Church is that if Scripture reveals that Mary is the Mother of the Word-made-Flesh, and the Word-made-flesh is God, then Mary is the Mother of God (the Word), not from eternity of course, but beginning in time and for eternity. To say only that Mary is the Mother of Jesus or only the Mother of Christ, is to subscribe unwittingly to the doctrines of heretics who denied the unity of the Christ’s Divine and Human Natures.
But is it in Scripture? Yes, in addition to the above way we find that God reveals to the heart of Elizabeth the truth about the Incarnation, God-made-flesh. When Mary arrives to assist her in her pregnancy with St. John the Baptist, on seeing the Blessed Mother St. Elizabeth declares,
“blessed art thou among women and blessed is the fruit of thy womb, how is it that the Mother of the Lord (mater tou kyrios) comes to me” (Lk 1:42-43).
In both the first half and the second half of this inspired address mother and child are inseparably united. In the first, Mary and the fruit of her womb, Jesus, are praised. In the second the unity of their relationship is revealed, as well as the unity of Christ. Mary is not merely the mother of Jesus the Messiah, somehow conceived, but the mother of the Lord. The text preserves the Greek, kyrios, although the language that would have been spoken was Aramaic. Among the Jews the name of God was not spoken, but a substitution was made to preserve respect. By convention when translating Hebrew and its sister language Aramaic into Greek, such as in the Greek Old Testament (Septuagint) used to evangelize Greek-speaking Jews and gentiles, the word substituted for God’s name was Kyrios, which we translate as Lord. This was in lieu of I AM, Christ’s use of which for Himself would later scandalized the Jews. Elizabeth would never have been so bold, however, instead calling the fruit of Mary’s womb, the Lord, with all the meaning which the Jews attributed to it and which the Catholic Church continues to understand of the Word-made-flesh in Mary’s womb.
It wasn't any kind of conspiracy or anything deliberately malevolent. In my view, and from everything I've read, it simply was an organic process that set in, and the more focus placed on Mary, the more important she became, leading to even more focus on Mary, etc. All of this set up a cycle of increasing attention paid to Mary, eventually justifying "prayers" to Mary and all the additional doctrines that came along after.
This does not remove the fact that it isn't a true part of Christianity, it's unbiblical, it takes away from the Son, it focuses worship (prayer, in my view, and the view of many others, is a form of worship) on the creature not the creator, and it's a big, unnecessary distraction in general. There is no historical basis for it. There's definitely no scriptural basis for it.
Yet, the intensity of devotion to "the Blessed Mother" indicates that this doctrine touches some deeply-rooted aspect of our fallen humanity. Something in us desperately yearns to avoid the face of God, to hide behind some lady's skirts. And "someone" -- perhaps God's original worship leader -- desperately yearns to be the focus of the attention and adoration only due unto God. This "someone" will even disguise himself as an angel of light -- or a heavenly queen -- in order to hijack those devotional energies.
There are both psychotic and demonic elements about the cult of the virgin, as well as the historical, pagan roots you so clearly delineate.