Here's how I would answer your question.
The prophecies are that there will be a great evil called the Dajjal who will, through seduction or arms, nearly succeed in taking over the globe -- but will be unable to take Mecca and Medina. The Mahdi and his army will rise up and do battle with the the Dajjal, his army, and his followers. They will kill every last one of them. Any non-Muslims who have good hearts will now convert and become Muslims. The entire world will be peaceful and prosperous under the just rule of the Mahdi. Some hadith say for 7 years, some for up to 40 years. After the Mahdi dies, then comes Judgment Day.
'Isa (the Muslim version of Jesus) fights at the right hand of the Mahdi during the battle, and is subordinate to the Mahdi. He rebukes and maybe kills all the Trinitarians, and levels all the churches.
The relevant point to your question is that, instead of waiting for a real one-eyed, world-conquering, miracle-performing giant to show up, many mullahs have decided that the miracle-performing is an allegory for the marvels of Western science and technology, that the world-conquering is the pervasiveness of Western culture, and that the one-eyedness is that pyramid on the back of the dollar bill.
They don't have to "fulfill" the prophecies. The prophecies have been fulfilled all on their own (to them). All they have to do is enlist at the recruitment station to join the Mahdi's army, and then go out and kill some infidels.