"However, another interpretation, equally possible and one which coincides more with the aims of this essay, is that Ueshiba became disenchanted with the transformation of his art from a band of disciples bound by deeply personal relationships into an impersonal organization that he could no longer control."
It would be interesting to know to what extent did the existence of a legal foundation actually constrained Morihei Ueshiba. It would be difficult to argue that the founder "became disenchanted with the transformation" if in practice he was free to continue to do with his art as he pleases.
In addition, 1942 was a turning point in the war in the Pacific (Midway , Guadalcanal). Given the strong connections with the military, Ueshiba may have been privy to this information and form an educated guess as to where things were heading, so another interpretation may be that he was just getting out of harm's way.