I ask because it seems as if he was unaware of the destruction of the temple.
Why would he write about the destruction of Jerusalem? He was writing about "what is now" and "what is to come".
Revelation 1:19 Write the things which thou hast seen, and the things which are, and the things which shall be hereafter;
Look at the "churches" he was told to write to. No "church" in Jerusalem? Jesus was sent to the Jews. He didn't address them at all? The only explanation is that they had already been dispersed and the Temple destroyed.