As heart-breaking as the situation on Har HaBayit is, think what would be the case (with Mashiach having not yet arrived) if that stupid domed structure were NOT there.
At best, it would be a big tourist site, with thousands of people, Jews and goyim, tramping through every area of this makom kadosh with their cameras just like they do at the back of the Kotel plaza.
At worst, the Israeli government or the Jerusalem city government might turn it into a sports stadium or a shopping area.
HaSh-m had a reason for allowing that mosque to be built there and remain there – temporarily.