My thoughts are they haven't figured out a way to bring in and retain new players in AH3 and so are launching the new game to keep their revenue flowing.
What if it is the very basic, core nature of AHIII that is preventing gaining and retaining new customers? Should they fiddle with the core payment model and open sandbox model of AHIII to try it out?
What if the new generation of players reject the two-week trial then pay us a subscription or Flake-Off model? What if that revenue model went out with 3.5" floppies?
What if the completely open sand-box, you're on your own to figure out what to do, play model isn't what new player want? What if they prefer a more focused, time limited, curated (micro-scenario) experience?
What about players who still prefer the old AHIII model?
Maybe you create two games sharing the same core technology and assets, but each allowed to present a model that two different populations of players want, so you don'y have to force either model of the other? There may not be one single model everyone one wants.
Why not re-package the same technology in two ways to pull in the revenue from two different populations?