There is one other possibility.
He might be trying to outdo Bush41 by barfing on the Emperor’s shoes.
Its a parody of a very deeply significant gesture in Japan. A mockery of Japanese culture, whether Obama intended that or not. Few Japanese have the privilege of bowing to the Emperor, and if this photo makes the news in Japan, it will be seen as a veiled insult, especially by the more conservative elements in Japan.
At this level of diplomacy, the game is played for keeps.
Obama has blown his whole visit.