Jerusalem was considered unimportant by Muslims until about 100 years ago, when some Muslim scholars decided that Muhammad tied his horse “Barack” to the Western Wall before flying with the horse from the Temple Mount to heaven.
The story in the Koran about Muhammad's night trip on the horse Buraq doesn't specify where the "furthest mosque" is. At least by the time of the earliest biographies of Muhammad, the Muslims had decided that the "furthest mosque" was in Jerusalem. The earliest biography was written by Ibn Ishaq, who died in the 760s. His original version doesn't survive but works based on it from the 800s and 900s do, so the legend connecting Muhammad to Jerusalem has been current for over 1000 years. I don't think the Muslims would have been so eager to get the Crusaders out of Jerusalem if the city had meant nothing to them. Obviously it's much less important to them than Mecca is, or than Jerusalem is to Jews and Christians, but the connection is not a recent invention.