Luke only quotes the part of the question that the disciples ask the Lord about the destruction of Jerusalem, not his second coming (i.e., the end times).

Luke 21:7 “Teacher, but when will these things be? (that not one stone of the temple shall be left upon another) And what sign will there be when these things are about to take place?”

How could we then conclude that the following verse is about the second coming?

Luke 21:25 "25 “And there will be signs in the sun, in the moon, and in the stars; and on the earth distress of nations, with perplexity, the sea and the waves roaring"

Is it possible these "signs" happened already in 70AD?