Walt Disney Animation Studios under its various names (original name: Disney Brothers Cartoon Studio) has gone through many defined cycles, which we term "eras." These cycles were often, but not always, caused by outside events such as wars and changes in society at large. Sometimes, the studio just paused to catch its breath - or temporarily lost its grip. Things happened, people retired, new people were hired, exciting companies with new ideas were acquired, the inspiration came and went in recognizable flows.
Genius is a pretty bird that flies around an empty room featuring an open window - sometimes it flies out, and we are left alone, bereft of its amiable company. And other times, to our delight, the bird unexpectedly finds its way back in again. But you can't capture the bird whenever you want to, for it flies in and out of its own accord.