If the world is a fair where vanities are sold, and if external appearance and manners are valued more highly than good character and ethical conduct, then it makes sense that those who can put on the best show in public end up winners. Vanity Fair is fixated on performance and the way in which we all act out roles for the benefit of those around us. The only difference is that most of Thackeray's characters do this kind of acting subconsciously (and thus, not particularly well), while his main protagonist, Becky, is a self-aware master of the stage.
Characters in this novel can be separated into three types: those who are purely authentic, both in public and private; those who have an authentic face or personality that only shows in private; and those who are so deeply caught up in performing their socially appropriate roles that they no longer have an authentic self at all. The novel shows us problems with each kind of existence.
Activity and performance go together in Vanity Fair. From the narrator on down, anyone engaged in putting on some kind of show for an audience is by definition working at making something happen. By the same token, characters who refrain from any kind of acting are passive and inert, waiting for life to happen to them. Although on its face the novel seems to endorse this kind of inactivity, in reality it is the – perhaps malevolently – active life that it values.