When Mary and Joseph bring the baby Jesus into the Temple as their firstborn son, a practice of presentation and ritual offering to God in gratitude and service, they hear from Simeon words of exaltation and they are amazed.
We shouldn’t hear this as surprise, though; not in the sense that they didn’t know this stuff about Jesus — they clearly did. They knew the work God was doing at least, and that Mary, as mother, was given an incredible honor. This, after all, was something Mary herself sung about when the angel offered God’s deal to her. There is little doubt that Mary understood that her giving birth was part of something greater and that God’s work is to liberate the oppressed and raise up the poor.
Mary hears this, the words of a priest filled with the Holy Spirit, however, and that Jesus himself is the culmination of the man’s work — perhaps waiting and anticipating. And Jesus as a light to the Gentiles and glory of Israel? That had to hit different. I don’t believe they are surprised by the liberative character of God, but are amazed by the scope and that their son, still just an infant, could be the whole thing, the centerpiece of the revolution, even that Simeon, too, can see what they see.