My take: Caldwell was fired now to throw a bone to the public due to the push-back on Lot J vis a vis the Jags poor performance. Khan is trying to show he is vested in the "quality" of the product the Jags are putting on the field as demanded by the Jag's fans.
Why not clean house at the end of the season? What's 5 more games at this point. Will he hire a new GM any sooner?
Maybe, but I don't quite think it goes that deep. I actually think this was a football move. Sure, Lamping was probably in his ear saying if the team was good this would be an easier sell but I think this came down to keeping up with the Joneses.
This year is looking like a record number of GM firings. The Jags were the 4th or 5th one already, and there's likely 3-4 more which is a tad high for a typical year (especially with that many already open).
I think they did it to get a jumpstart on candidates/not allow good candidates to get taken.
What will likely happen is the new GM will have say over the new coach, so I don't think Marrone is going to be here in '21.
To me the only advantage to dumping a coach mid-season is either if the team has quit on him (which hasn't happened), or you want to audition an assistant for the permanent job (which is unlikely). You're going to get very few coaching candidates to talk to you mid-season (mostly because if they have a job it isn't allowed). GM candidates on the other hand would be easier - there's a higher possibility of getting a good candidate that's not with a team right now, plus it's a little easier to have an off the record convo with a GM candidate vs. a coach.