John Lasseter's spiral into alcoholism and sexual harassment in part fuelled by an out-of-control ego also didn't help Pixar's fortunes.Worth keeping in mind - every Pixar film released in recent years, including the just-released Lightyear, began development and production under Iger's watch. Pixar's significant decline started only a few short years after the aquisition, really only once they started releasing projects Iger had a hand in. If anyone is responsible, it's the man who bought it.
I don't really say that in defense of Chapek, but it should be remembered that their 4 projects released under his tenture were pretty far along by the time he showed up. We haven't really seen his touch on their movies yet.
I honestly don't know how directly Iger meddled in the films and to what extent we can attribute him for the quality of films released under his tenure. If we're crediting him with the declining quality of Pixar films, are we also saying Walt Disney Feature Animation only really turned around when Iger started having a hand in the films? Should we also be patting him on the back for the massive success of the Marvel films?
I'm not saying that to be antagonistic, but honestly I don't know how directly he did meddle in the creative decisions of each division. The impression was that he was more hands-off than Eisner and let people do their own work, which people have been criticising in terms of him being less creative than Eisner in this thread. It can be both true that he didn't interfere creatively in Disney's output but did make decisions that impacted quality, but I would want to hear some account of how that worked before just assuming it in specific cases such as Pixar.
One of these articles had an ex-Imagineer describe the differences in working with Iger and Chapek which I thought was interesting. He did characterise Iger as trying to push and negotiate a little more on timelines and budgets for projects, whereas Chapek would just kill an idea dead if it did't fit what he wanted. So, that could be something of a difference in management styles that will have an impact on creative decisions.