Hints are there, plentiful even, and it's fairly easy to draw conclusion that something bad will happen if SH does indeed do the deadly deed. But it's not quite as obvious as say stealing the idol of Silvanus (foreshadowing). Sundering the moon dome is nice and cinematic and fair enough, but it could have easily been something else just as unexpected - like phantom dark justiciar followers. And then we could well be head-canoning reasonable rationale after the fact.
Personally, I think CR's meta explanation in post 2 hits closest to home. And I'm okay with that. One of the themes of being evil is the expedience factor, and killing off side-quests moves you that bit faster to the finale.
