Guy Gardener wrote:
The time ship wasn't "destroyed" it was "removed from time".
Which makes the whole story one big meta-grandfather. It was a grandfather paradox in meta-time. So just to make this cute and neat story they implicitly introduced meta-meta-time. They didn't go back in time to change it, they went back in timeline changes and changed them.
I think that the time ship was destroyed in one big plausibility explosion.