Scholars are divided over when Mark was written. Some think the gospel was after the temple’s destruction in 70 AD by a Roman Army. Some think it was written before. It was one of the largest public buildings in the Ancient World, much larger than the Acropolis, for example. If you go to the Wailing Wall, you can see the massive foundation stones that so impressed the disciples. (I am leading a trip this year!)
The Temple dominated the landscape and the religious imagination of the people. You can see evidence of this in all the Psalms that mention the Temple. (Psalms 120-134, for example, were written to be sung on the way to the Temple.) Put crudely, the idea was that some Jews at the time believed that God inhabited the Temple and would protect the city and the people. A Rabbi I love once taught me that modern Judaism (he was a Reformed Jew) traces back to a rethinking of Judaism following the destruction of the second temple (Solomon built the first and Herod the second). There has been additional development of Jewish thought since the Holocaust and the establishment of the modern State of Israel.
Anyway, given the Temple’s importance, Jesus’ prediction of its destruction likely caused a stir. Some believe it encouraged early believers to flee the Roman siege (the abomination). Given that Temple dominated the religious imagination of the people, Jesus instruction that this is not the end has special relevance to the first readers of the gospel. Perhaps we can learn that just because the big things in our lives are torn down does not mean God is finished.
John Calvin claimed that Mark’s gospel emphasizes Jesus as prophet (whereas Matthew and Luke emphasize Jesus as King and Priest). We saw this at the beginning with the prophet Isaiah’s commentary on the prophet John. We saw it with the angel’s provision for Jesus in the wilderness (similar to God’s provision for Elijah). We saw it in Jesus’ transfiguration, where Jesus appears with Moses and Elijah.
Did the affront of Jesus’ prophecy about the temple prompt the abuse in Mark 14:26, where people blindfolded, struck him, and demanded that Jesus prophesy? Notice that immediately afterwards, Mark tells us that Jesus’ prophesy about Peter comes to pass.
Scholars have wondered about the Mark’s abrupt ending. So did the early church, which is why your translation probably includes an ending that is identified as not original and later. Skeptics have seized on the short ending to claim that the resurrection tradition developed later. This is surely not the case given how, from the beginning, the disciples made extraordinary claims about Jesus (Son of God) and made extraordinary sacrifices to follow him.
There are other possible ways to read Mark’s ending. One that I find persuasive is that the ends of scrolls were fragile and Mark’s ending is lost. Some scholars suggest that at this point we can turn to Matthew and find Matthew’s embellished version of what was Mark’s original. Maybe. Or maybe not. We don’t know.
The ending we do have (whether intended or not) is suggestive. Mark ends with the risen Jesus’ promising to meet everyone in Galilee. A rendezvous in Galilee would overturn Jesus’ crucifixion and signal a resumption of Jesus’ kingdom ministry. That the closing line tells us that the women fled in fear, invites us to imagine what happened next and their obvious faithfulness (because we have the gospel!). It invites us to consider how we might respond to such good news.