I don't think the left side of our defence was that different last season. We added Graves and most likely subtracted Kulikov and Murray (for now). This trade could be indicative of them wanting to bring Kulikov or Murray back, I guess. I just would feel better with Butcher being the 7th D than Bahl or some other kid who may need AHL seasoning. For that reason, I'd imagine the team has another LD in their sights.
I get the mental part, but every season there are many similar aged defencemen who suffer the same fate. It's just the business this is. I know Siegenthaler was one with WSH- he requested a trade, but the Caps still got a decent return. Now, I imagine this trade was made preemptively to adjust for another signing or move, which makes more sense. But if not, it would've been wiser to hold Butcher and maybe try to net an asset, without retaining salary, when the season starts and injuries occur to other teams, or possibly our own (hopefully not) . Once again, I need to reserve my judgement on this deal until we see what else Fitz may have in place, but if no other move is made to acquire a veteran LD, this trade likely seems pointless.