The "IT" factor is a subjective attribute IMO. For me, Grigor has it, so does Thiem and Kyrgios. Zverev, not so much, I find him dull, actually.
Some fans were laughing here on this forum at Carreno-Busta or Sock a few years ago, when they were on a temporary plateau and seemed like some journey men.
But recently, they both climbed into relevance, and now both pressed into the top 20 (Busta will 3nter as of newt week). And because the players these days are peaking towards late twenty- or even later, both could become serious contenders on a regular basis, if they keep growing.
They could easily lose today and be a single opportunity for them in this event, but I do think they will have many more in the future.