One interesting factoid that the new york times did not mention is that while it was common for emperors to resign before the meiji restoration, a lot of those resignations probably were not voluntary.
The Japanese emperors are the longest reigning royal dynasty in the world, having reigned for the entire known history of the nation. But perhaps heir secret is that they did not have much power most of the time.
During the time of the shoguns and even before that it was common to force an emperor to resign before he reaches adulthood so as to ensure that there was a child emperor on the throne at all times. A child emperor of course is unlikely to use his position to seize power.
The Meiji restoration was a revolution whose stated goal was to restore the power to the emperor. Perhaps it was in view of that goal and the history of forced resignatons that they made a law that did not even give the emperor the option to resign. However, I am not certain whether the present emperor for life law dates back to the meiji restoration.
Or perhaps they put the law in after WW2 to ensure that foreign governments do not mess with the emperors.