This year's Madrid Open has seen multiple matches finish in a final-set tiebreaker with China's Zhizhen Zhang prominently featured as he won three consecutive like that.
Zhang is enjoying a breakout event in Madrid as he was able to take down a few notable players including Norrie and Fritz in the last two matches he played. Both of those victories came after a 3rd set tiebreaker which is actually the way he won the last three matches in which he played in Madrid. This year's event is featured a lot of these decider tiebreaks, far more than in the past even though it's quite common in general.
Zhang explained his run like this:
“I think here the altitude is helping me for the serve because big serves are helping me to hold the service game. That’s why there are so many tiebreaks I played. Even if I couldn’t break the guy, I still won the match because I’m holding my service game into the tiebreak. In a tiebreak, nobody knows what’s going on. (It’s) just a few points difference.”
He's not the only player that was able to win matches in that way. Players like Tsitsipas, Lajovic and Coric also did it that way. So far we've seen 11 decider tiebreaks so far with 7 matches still to be played. There is a very good chance that we see a couple of more. This mark is already a new record for an ATP 1000 event.
Madrid's high altitude contributes to this as the ball flies faster which helps big servers. More or less all top players are pretty good servers as the game has been trending that way. It's arguably the most important shot and the only one you can fully control.