What do you mean by “famous?” My first thought was famous within the fitness industry, which would in most cases be fitness educators of well-known programs. And in order to teach others those programs and be a CEC provider, yes, they’re going to be certified by ACE, AFAA or both.
As soon as you define fame to mean known outside the industry, there are “fitness celebrities” who have ACE certification plus much much more. Sadly, there are also a lot of people who are well known but don’t actually know all that much.
There was a recent article posted on this site called “certification by selfie,” implying that these days, looking good and being adept at social media can get you clients, regardless of whether you can actually teach others or if your methods are safe, effective, and sustainable.