I dunno. Is it really "big but not too big" when the group is one of the top groups/sometimes arguably the top group (talking about Exo here)? Every management ever has made bad decisions relating to their artists, sometimes they just suck and sometimes it can be hard to tell what will lead to the best result in the end. Hindsight is 20/20 after all. So in general I feel that it's not as simple as SM didn't make this one Exo choice well in hindsight, that means they hate Exo and are sabotaging them. The only time sabotaging would make sense to me is if SM knows they're planning on suing them for work stuff or things like that to avoid repercussions.