Needless to say, that's a championship effort and catch by Cubs first baseman Anthony Rizzo (who also homered in the road half of the same frame). However, his catch-and-tumble carried him out of the field of play, which, as Cubs play-by-play man Len Kasper explained, means all base-runners automatically advanced. Since David Peralta was on third, he came home with the go-ahead run. As you can see above, the D-backs would go on to win by that same margin.
Outcome notwithstanding, it was an excellent snare by Rizzo, and he can't be blamed for making an such an instinctual hustle play and brilliant effort. Still, if Rizzo and the Cubs could go back in time, he'd probably let the pop foul drop for strike one.