Hollywood tends to pay a lot of attention to CinemaScore (very roughly: exit polls of people seeing it on the opening night), and The Rise of Skywalker got the lowest CinemaScore (B+) of any live-action Star Wars movie - lower than Solo and the prequels. "They audience liked it ALMOST as much as the one with Jar-Jar!" is not what Disney wanted to hear, especially since that sort of thing will have huge flow on effects to the ongoing revenue stream (toys, theme park rides, merchandising). For example, I believe the newest Star Wars ride has sharply underperformed, and Disney leadership will probably believe (correctly) that the poor reception the latest movies got was a driving factor.

And the box office take, while still very substantial, was underwhelming for what was meant to be the crowning glory of a 40 year franchise, and compares poorly to other end movies for big franchises.

The "point" of buying Lucasarts from Disnye's point of view was to apply a lot of money and some of the magic they've used on the Marvel franchise to make a truly vast amount of money, get a bunch of critical acclaim, and set up the franchise as a money spinning machine that will keep filling theatres for spinoff movies every year forever. Instead they merely made a very large amount of money, the critics said the last movie stunk, and the fanbase seems deeply disinterested in more movies, which had led to them cancelling a bunch of planned movies.

It's not that bad, and I'm sure it's fixable, and the Mandalorian is doing great, but MAN is it less than what they were hoping for.

(And persistent rumours have it that Iger intervened directly into the creative process of The Rise of Skywalker late in the cycle. If true, that makes the disappointing TRoS results reflect on him...but I obviously have no idea if that's true.)

That being said....I don't think Star Wars was bad enough to trigger this. CEOs typically can do much worse for much longer, and as others have noted, the choice of replacement (and the speed of the replacement) is mystifying. I would guess ill health, or maybe some sex scandal rather than poor performance being a factor.

Regardless, I don't think they're that upset. Star Wars hasn't been a home run, but it's been a solid double and net positive to Disney.

One can only hope that people finally get enough of the merciless milking of franchises.

This cause lots of major talent such as Lawrence Kasdan, David Benioff and D.B. Weiss to leave the franchise.

Benioff and Weiss were slated to do a whole new trilogy for Star Wars, but they suddenly realized they didn't have time.