I've always wondered why Chapek was picked. It seems that CEO often choose head of the most successful division as successors (e.g. Amazon's Jeff Bezos choosing then-AWS chief Andy Jassy as CEO). Meanwhile, Disney parks invested massively into the struggling initiative of digitization.
Additionally, Chapek's timid personality did not seem as conducive in the people-centric entertainment industry.
Bob Iger was a tremendously successful CEO. CEO’s tend to have big time egos, and successful ones seem to not like the prospect of being outdone by their immediate successor. Perhaps it is similar to the phenomenon of presidential candidates picking lackluster VPs for their running mate?
If you really want to think in a Machiavellian way, perhaps Iger hand picked Chapek to act as a fall guy so that market pressure would hit the stock during his watch and not spoil his own tenure.
The most likely thing is that Chapek was simply seen as failing to maintain all the growth Iger managed to deliver and they want him back in order to try claw some of that stock price back.
Additionally, Chapek's timid personality did not seem as conducive in the people-centric entertainment industry.