RESPONSE: You did some good historical research, but the answer to the question of how Mark (c 70) contained a prophecy of the destruction of Jerusalem remains uncertain.If it's a problem, it didn't originate with Matthew, because Matthew was copying Mark, whose Gospel was the first to introduce Jesus's prophecies about the fall of Jerusalem and its possible relation to "God's end-times schedule".
Mark's Jesus, not Matthew's, was the first to announce the coming fall of the capital city.
www.thoughtco.com/the-gospel-according-to-mark...
Jesus Predicts the Destruction of the Temple (Mark 13: 1-4)
Jesus’ prediction of the destruction of the Temple in Jerusalem is one of the most important features in Mark’s gospel. Scholars have been sharply divided on how to deal with it: was it a genuine prediction, demonstrating Jesus’ power, or is it evidence that Mark was written after the Temple was destroyed in 70 CE?
New American Bible: Footnote to Mark’s gospel
Modern research often proposes as the author an unknown Hellenistic Jewish Christian, possibly in Syria, and perhaps shortly after the year 70.
rosetta.reltech.org/TC/v13/Head2008.pdf
The Greek text of the Gospel of Mark is certainly the worst attested of all the canonical gospels. It is extant in only three papyrus manuscripts, none of which are by any means complete, and of which only one ( 45) is definitely earlier than the fourth century uncials;1 while one other is perhaps contemporary with them ( 88).2 Thus our knowledge of the text of Mark is more dependent on the early uncial texts than is the case with the other gospels, where early papyri and more substantial comments in church fathers supplement the early uncial texts.3
