So did God choose Mary because He knew she would be the only human ever to exist to choose not to sin, or did God create Mary special so that she wouldn't sin? Or is it just a coincidence that Mary happened to birth Jesus and choose never to sin? Talk about the stars aligning.
That's hard explain: you'd have to work out how God's omniscience and sovereignty interact with human freedom, and that's out of my league. (I'm not preternaturally bright!)
What we do know is that the people we see around us today, ourselves included, are "subnormal": we all have heritable defects. These defects are many, but the most important ones are that we have darkened intellects, weakened wills, and distorted drives and appetites; and thus we lack an "automatic" harmonious relationship with God.
It was not so from the beginning. God did not create Adam and Eve with these defects. He created them good (as Genesis says) and He created them "normal" --- with what is called "Original Integrity" or "Original Justice."
This is the perfect human nature everybody would have enjoyed, as descendants of Adam and Eve, if they had not sinned. As it is, they did choose disobedience --- sin --- and all of its consequences. Since Adam and Eve were the progenitors of all mankind, we their descendants inherit their fallen nature. We became (Eph 2:3) “children of wrath.”
But God somehow preserved Mary from inheriting this abnormal nature. The early Fathers of the Church-- here I'm thinking particularly of Irenaeus, and Ephraem the Syrian --- reflected a lot on how Mary was the new Eve. That link is really worth clicking on, if you want to understand their line of thinking. Or is it just a coincidence that Mary happened to birth Jesus and choose never to sin?
Coincidence? No, she just made the right choice (humility and obedience), unlike Eve, who made the wrong choice (pride and mutiny.) And because Mary was unblemished by any of the foulness of sin, she was fitting to be the person who would transmit a human nature tot he Word made flesh, God's all-perfect Son our Lord.
Talk about the stars aligning.
Not sure what you mean by that, but yeah, everything did line up just right. Scripture calls it "the fullness of time." And there was even, as I recall, a star!
P.S. to the others I've invited to listen in: have y'all got anything to add, here?