Hiraizumi is located in the Tohoku prefecture of Iwate, which was heavily hit by the tsunami. While inland itself, Hiraizumi is only about 30 miles from the coast, not far from Rikuzentakata and Ofunato, names that are now familiar in Japan from the news reports on the terrible destruction there. This decision is a major morale boost for the people of the region. It's being regarded as a symbol of the reconstruction of the region, and residents hope this will help bring the visitors back into the area.
Due to time zone differences, this ruling was passed during the night in Japan, so most people there haven't heard the news yet. What a nice surprise to wake up to!