Wiktionary
that was it
phr. finished. There was nothing more to the issue.
Usage examples of "that was it".
There were only a few bottles of real liquor left in the village four rye, three Scotch, three brandy, nine real wine and half a bottle of Drambuie belonging to old McIntyre (only for marriages)and when those were gone, that was it.
So he does some singin' and rubs powder on my mouth and mutters and touches me, and that was it.
Alen ran through the chapter in his mind, puzzled, until -- that was it.
The moo-shu pork at the back of the fridge might have been too old, but I don't think that was it.