It would have been better for original Wolverine to vanish with the original timeline. Why not? Everyone else from the original timeline was gone. Why not him?

It may have been worth the sacrifice, but the film doesn't acknowledge the sacrifice at all. it glosses over the other version of Wolverine so we could have a happy ending. I doubt the writers even realized what it meant to have the original Wolverine reappear.

Making for a weird happy ending.