There's no way of knowing so it's pointless to speculate.
We know the 1st half was tough and they lost a lot, we know the 2nd half was easier and they won a lot.
I see scheduling as the biggest factor in the 'turnaround'. Did personnel changes help? Who knows, I'm not willing to fully admit the changes worked when other factors were also in their favor.
I think coaching is overvalued in most sports, including football. Talent/endurance/effort/execution typically matter much more IMO, so I don't put much stock in coaching changes anyway. If this is a move to keep talent (CJ) around and the locker room together, then it's probably the right decision.
For what it's worth, I would've been fine with a total rebuild. I'm not a big fan of patch jobs and retooling when the opportunity to start fresh is there. I don't think this current team is capable of winning a championship and I also don't think they have a young core in place (yet) to build a championship team...too many high picks not named Ansah have not had a huge impact. I think this moves buys them immediate (and minor) success, but will ultimately not make a difference 5 years down the road. Whether they kept Caldwell or hired a new HC, I think Quinn has the same job ahead of him. I see a temporary boost to 2016, with little regard for the following seasons, which makes sense for 90+ year old owner.
That post was probably all over the place.
TLDR: Caldwell good for 2016, irrelevant past that