If they fire Kennedy just because the fans want her gone, and it turns out the bad decisions were coming from someone else or were forced on her by someone else who does the same thing to her successor, then firing her would make no difference.
It seems like you're starting from the position that Star Wars and its CEO are doing just fine, and throwing defenses at the wall like spaghetti to justify Disney not making any changes. Which, if that's your opinion, that's perfectly okay, and I won't debate you on it. I'm just pointing out that for those who don't like the way things are going, it's perfectly rational to hope for changes, even it that process incurs a bit of short-term pain, and even if it doesn't ultimately produce the hoped-for result.
By saying you "don't understand" that thought process, you're seemingly either making a near-zero effort to understand it, or you're using a dishonest rhetorical trick to imply that it's so irrational, no right-minded person would adopt it.