Reading between the lines, it seems like the bigger question is why hire directors known for improv and having their own style when Kasdan felt his script needed read word for word and done his way?
It really seems like Kennedy/LucasFilms don't have a clue what they actually want from these spin-offs, and continue not to figure it out until very late, then force these up and coming directors into crazy reshoots and creative retooling, which effectively negate the point of hiring that specific director in the first place.
You just don't get this far into filming and suddenly realize it's "too comedic".
I think there's an even subtler reason their process might've clashed with Kennedy and co. A lot of comedy directors are well known for playing loose with things like coverage and line readings on set.
There tends to be a lot of "Ok, try it this way. Great, now try it that way. Wait, here's an idea! Why don't we...". That's in addition to all the writing on-the-go/improv/happy accidents that occur on set. The end result is that very few "locked-in" choices get made during filming, and instead a lot of the heavy lifting occurs in the editing room (almost like a final "rewrite). It's not laziness either. It's a legitimate process, and it works.
But when you're dealing with a $250 million+ blockbuster, and it's not immediately clear how the dailies are intended to cut together or what tone they're supposed to take? It doesn't necessarily mean the film is doomed - but it's definitely enough to get a risk-averse producer shaking in their boots.
I agree, though. You'd think there would've been more foresight - provided this isn't some sort of fuck-up on Lord and Miller's part.