When I look out in the audience during any promotion's crowd shots (WWE, AEW, TNA, WCW, ECW, NJPW, Lucha Underground, indies, etc) I always check the kind of shirts people are wearing. Who is the most popular star that connects with the audience, who has the coolest looking merch that fans actually spend their money on, that kind of thing. A wrestling tee is the most basic fan support signaling. If CM Punk's gear is all over the crowd, then you know he's still poppin' despite all the controversy. During the late 90s, it was guys like Austin, nWo, Sting or D-X. Other times, a current star will get some push & short-term popularity, so their merch sell fairly well but eventually fizzle out (Carlito, The New Day, AJ Lee, Dolph Ziggler, Becky Lynch, Finn Balor, Alexa Bliss, Daniel Bryan, etc.). Then you have the niche-but-viral shirts that become popular through sheer nerdcel word-of-mouth like the Bullet Club/Young Bucks/ICP etc.