there's a new rule implemented for this season. i couldn't find too much about it, especially not in english, but a bit similarly to the premier league, var can be called when there's an obvious error or an unseen event.
there are 4 cases of obvious errors and unseen events: goal given/not given (it's not only the goal line technology; includes cases when there's a foul in the build-up or there's an offside to be reviewed, etc), penalty or not, direct red card, wrong player given a card. and here's the twist: these cases can be reviewed if the ref couldn't see the case properly. now, in this case, the ref could see the case, he awarded a free kick to spal, and gave a yellow to rabiot for simulation. the latter is important: if there's no yellow to rabiot, var couldn't intervene, because the ref saw what happened, period. but since he gave the yellow to rabiot, and var suggested that the ref sanctioned the wrong player, var ref could call for the review.
it's kinda stupid rule, i know.