Now, I know that there is no way to prove the reconstruction I laid out but it does explain the odd flow of the section. Shifting from literal to metaphor, it also allows a possibility that an UrMark (early form of Mark) was written before the events of 70CE.
It's also perhaps relevant that the Gospels dance around a Messianic expectation that the Messiah would rebuild the Temple, (as we also discussed recently) and that language could have been easily reinterpreted as predicting the destruction of the Temple in 70CE.
I favor the idea that the early form of Mark included the standard apocalyptic language as it associates pretty well with the Son of Man motif that recurs throughout Mark. It is also simpler to suggest that an editor 'clarifies' and elaborates the older cryptic language than to see that prophetic language being secondary.
If that is so, then a redactor had only to very slightly modify 13:1-4. They simply removed the Messianic claim to rebuild the Temple. It could have read something like this:
As Jesus was leaving the temple, one of his disciples said to him, “Look, Teacher! What massive stones! What magnificent buildings!”
2 “Do you see all these great buildings?” replied Jesus. “Not one stone here will be left on another; every one will be thrown down. and I will build it back in 3 days.”
3 As Jesus was sitting on the Mount of Olives opposite the temple, Peter, James, John and Andrew asked him privately, 4 “Tell us, when will these things happen? And what will be the sign that they are all about to be fulfilled?”
The earth will quake, darkness and distress, pestilence and famine, the nations will roar like the sea. The sun will be darkened, and the moon will not give its light; the stars will fall from the sky and the heavenly bodies will be shaken.’
At that time people will see the Son of Man coming in clouds with great power and glory. 27 And he will send his angels and gather his elect from the four winds, from the ends of the earth to the ends of the heavens.
This then would flow into the subsequent narrative of the arrest and charges of blasphemy for claiming to be the Son of Man and to be the one who will rebuild the Temple.
After the events of 70 and 135CE the words might have taken new meaning. Hadn't he predicted the destruction of the Temple? But he couldn't have predicted to rebuild it, as this didn't happen. To deal with this the redacted Mark and Matt say the claim to rebuild the Temple never happened, it was a lie, John on the other hand dealt with this through the improbable suggestion he was referring to his body as the Temple.
Given the time that had past and the different nature of the 4th Gospel, it dispenses with the whole section. In fact, I suspect the author is chiding some who believed Christ was to immanently return to earth in some dramatic display.
John 16:
16 Jesus went on to say, “In a little while you will see me no more, and then after a little while you will see me.”
17 At this, some of his disciples said to one another, “What does he mean by saying, ‘In a little while you will see me no more, and then after a little while you will see me,’ and ‘Because I am going to the Father’?” 18 They kept asking, “What does he mean by ‘a little while’? We don’t understand what he is saying.”
19 Jesus saw that they wanted to ask him about this, so he said to them, “Are you asking one another what I meant when I said, ‘In a little while you will see me no more, and then after a little while you will see me’? 20 Very truly I tell you, you will weep and mourn while the world rejoices. You will grieve, but your grief will turn to joy. ...25 “Though I have been speaking figuratively, a time is coming when I will no longer use this kind of language but will tell you plainly about my Father.
The writer had effectively negated the whole topic as figurative. In some spiritual sense Jesus would be present with his followers, this text alone is not clear.