Right you are, though I don’t remember killing him and there’s nothing in the Combat Logs indicating that I did.
This leads to an odd situation. This Ent has no “Village” left to control as it’s been blighted, so I assume I can’t ever control it. It’s a freelancer wandering the woods and heading to the site of a future nasty battle, but probably not in time to do me any good.
In practice, wandering Ents in particular are pretty hard to get control of because they’re so slow. It’s possible, though. Any neutral unit that’s been displaced will, upon regaining control of itself, walk to the nearest unblighted settlement. If a player controls that settlement, the unit will join that player’s forces automatically; otherwise it’ll join up whenever someone claims the settlement.