Christianity’s supersession refers to its inextricable relation to and eventual emancipation from Judaism.
The former asserted itself as an upgrade, an improvement on the latter. Supersession is a bond of heritage and of rejection.
At the millennial dawn, the Temple was a historical-physical institution loved by Jesus and the rest of the Jews. Jesus himself was Jewish.
In Luke 2, Mary, Joseph and Jesus make a pilgrimage to the Temple — but his parents lost the young Jesus in Jerusalem! He was tracked down in the Temple, where he remarked, “Why were you searching for me? … Didn’t you know I had to be in my Father’s house?” (Luke 2:49)
Despite this account's glaringly questionable historicity, it emphasizes something very important abut early Christian identity: it placed its win origins squarely in the Temple, in sync with Luke 2:49.
Jesus' early followers believed in his message but remained definitely Jewish in their customs, their monotheism and their attachment to the Temple. However, Christianity’s sense of self, of separation from the mother religion, was sowed when Jesus protested the Temple's commercialization.
This was the first act of animosity between Judaism and infant Christianity. “He also poured out the coins of the money changers and overturned their tables. He told those who were selling the doves, ‘Take these things out of here! Stop making my Father’s house a marketplace!’” (John 2:13-16)
Jesus’ followers would later see themselves as modified Jews — they perceived faults in Judaism, and saw the prophet Jesus as a guide to correcting these errors.
Jesus foresaw the destruction of the Temple (Matthew 24:1-2) but by means of a clever riddle asserted that he himself was the Temple (John 2:19).
Jesus was not antagonistic to the Temple, it was a cherished institution, but he saw it as polluted by impious entrepreneurs.
YHWH’s wrath would inevitably strike it down.
Jesus’ message was a rebellion. However, any hint of revolt in Jerusalem could prompt Rome to demolish the city. To maintain the status quo, Jewish authorities in Jerusalem had him executed.
However, Jesus’ death allowed for that essential part of Christian legend: His resurrection. The legend is true in at least one respect: through mourning his loss, his followers gave Jesus an eternal life.
Through their tears, the rational world was cleansed from their eyes.
Jesus' followers now saw an immortal Jesus, a theophany -- but they were still fully Jewish in every other way.
Yet this proto-Christianity was not fully independent: though able to garner followers to its Messianic Judaism, Christ’s followers were firmly under the customs, traditions and household rules of the mother religion.
When Roman hammers smashed down the Temple, they broke the bond between Judaism and Christianity.
At first there was simply a Jewish group adoring Jesus as a son of David who could reclaim Jewish national sovereignty. But now Jews were left at the same place that Ezekiel and Jeremiah had been, wondering what now without a temple?
The Jews remained tearing their robes, mourning the Temple. Christians saw the destruction as a divine condemnation – but Christianity was not damned, as its identity rested in Jesus anyhow.
Jesus’ followers, especially Paul, promulgated the notion that Christianity could supersede from damned Judaism, an anathema.
Christianity was thus emancipated, and took shape, expanded, evangelized, rose like leavened bread. Judaism and Christianity became categorically different, a relationship of heritage rather than oneness.
As Christianity succeeded and Judaism remained in turmoil, the destruction of the Temple came to be seen by Christians not just as a criticism of Judaism but a divine validation of Christianity.
Free from the Temple fixation, and with the Messiah in their hearts, the Christians shed the vestiges of their Jewish identity and went out to evangelize, not to mourn.
As he approached Jerusalem and saw the city, he wept over it and said, “If you, even you, had only known on this day what would bring you peace—but now it is hidden from your eyes. The days will come upon you when your enemies will build an embankment against you and encircle you and hem you in on every side. They will dash you to the ground, you and the children within your walls. They will not leave one stone on another, because you did not recognize the time of God’s coming to you.” Then he entered the temple area and began driving out those who were selling. “It is written,” he said to them, “‘My house will be a house of prayer’; but you have made it ‘a den of robbers.’"Luke 19:41-46
The שבת shabat restrictions give rise to a common argument against the Judaism of the era.
Recall how Jesus was pursued by the Pharisees on the score of his healings on the Sabbath day; Matth. 12.10 ff.; Mark 3.1 ff.; Luke 6.6 ff, 13.10 ff., 14.1 ff.; John 5.1 ff., 9.14 ff." [This is in reference to Mishna II § 2.10 where it is restricted to bind one's wounds on שבת shabat.] Strack, p 257
Christianity's supersession from Judaism can be compared to Islamic tahrif.
Tahrif is the notion that Judaism and Christianity had been corrupted over the years. Rather than building upon Judaism and Christianity, Islam viewed itself as a return to Abrahamic, ancient monotheism.