He didn't answer the first question, but did answer the second.
read all three accounts he answers both it just overlaps. Look at what Jesus is talking about when it starts
“And Jesus went out, and departed from the temple: and
his disciples came to him for to shew him the buildings of the temple. And Jesus said unto them, See ye not all these things? verily I say unto you, There shall not be left here one stone upon another, that shall not be thrown down.
And as he sat upon the mount of Olives, the disciples came unto him privately, saying,
Tell us, when shall these things be?
and what shall be the sign of thy coming, and of the end of the world?”
Matthew 24:1-3 KJV
“And as he went out of the temple, one of his disciples saith unto him,
Master, see what manner of stones and what buildings are here! And Jesus answering said unto him, Seest thou these great buildings? there shall not be left one stone upon another, that shall not be thrown down.”
Mark 13:1-2 KJV
he’s talking about the destruction of Jerusalem and the temple the siege of the Romans which happened in ad 67-70 fulfilling the prophecies about it
but they also ask about his return and the end of the world.
he answers both it’s just overlapping and the narrative breaks a couple times. It’s a lot clearer if we examine all three accounts Matthew mark and luke.
it’s a reference to the end of the Old Testament and also a reference to the end of the world when he returns.
but thats only My own view of anyone wishes to consider it.