Why was Issac Luria such an important rabbi?

Because in two short years he revolutionized both Kabbalah and the concept of Jewish religious leadership. He came to be identified as the central figure of the kabbalistic revolution in Safed during the second half of the sixteenth century. His centrality was twofold, as the initiator of a new school of kabbalistic thought known as Lurianic kabbalah and also as the primary figure who initiated many new religious practices and traditions that became widespread throughout the whole Jewish world.