I think the general feeling in the public was that the season wasn't satisfactory at all and you couldn't really be sure whether Rose really got the best out of the squad, but because of the various side issues it was okay to give him another season to prove himself.
And I think the bosses shared that feeling, because they committed heavily to Rose time and time again in the press and because Rosexit came as a complete shock, without a single hint even from Bild.
So it doesn't look like they made him out to be a scapegoat or even straight up sacked him, but rather that they wanted to discuss the various issues with Rose in their analysis meeting and then things got to a point where one or both parties said it might be better to go their separate ways.
For all we know it might have been Rose himself, who didn't want to continue, because it would be better for his career/reputation to quit after having reached second place, rather than go into another season and rebuild with a management that already had some doubts about him.
This theory is also supported by the communication from both the club ("BVB and Marco Rose are ending their collaboration" instead of the "Borussia Dortmund have parted company with Lucien Favre") and Rose himself:
I also don't see a strategic issue in switching coaches: Terzic's style is similar to what people wanted to see from Rose. Adeyemi should be a good fit, Özcan hasn't been finalized yet (so Terzic could object if he felt the need to) and Sülinho/Schlotterbeck are the kind of players, who aren't tied to a particular approach at all. The only question - and it's a pretty big one - is whether Terzic is actually a good enough coach.