The difference is that NTT lost money for years offering wholesale fiber below cost: http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.489... (pages 11, 16). It could do that because it has a national near-monopoly in the wholesale space (it get some money from every subscriber, no matter what ISP they use), Japan's economy offers much lower returns than the U.S.'s (making low return infrastructure investments relatively more attractive), and NTT is 1/3 owned by the government (which ordered it to deploy fiber, regardless of profits).