Why do you think it has something to do with not "competing against itself"? I mean let's be honest... thus far in the past two years they've released just 4 adventure books. 3 were in the Realms, 1 is now Ravenloft. They really haven't had the
opportunity to compete against themselves even if they wanted to, based upon their publishing strategy.
Let's not forget... we're still just coming up on the end of Year Two of what I suspect was meant/hoped to be AT LEAST a 5 year (if not 6, 7, 8) publishing plan. If we're looking at the overall timeline of 5E... there's still *plenty* of time for them to slide over to an Eberron book, and/or a Greyhawk book, and/or Planescape or whatever. If we knew that their next 3 books following Curse of Strahd were going to be in the Realms, then sure, we'd be able to look at it differently and with a little more of a critical eye. But right now we're not even halfway (if even a third of the way) through 5E's life cycle. Time is on our side.
But if everyone's still getting up in arms right now even though they've
just released a "Non-Realms" book, and for all we know have another "Non-Realms" book on the docket for release next (which is entirely possible-- heck, CoS just dropped in a Greyhawk Easter Egg, which could easily be a route back into GH if we follow the egg)... then people are getting bent out of shape prematurely and unnecessarily.
Not that... I'm really... surprised... by that of course. We *are* talking about gamers after all.