Wesley Mouch probably has the most appropriate name in the book, since he's basically a moocher. He rides other people's coattails into positions of power and influence, then proceeds to do a terrible job.
Mouch is sort of the captain of the looters, maybe even more so than the always-panicking James Taggart. This book features a revolving door of villainous characters who aren't very well sketched out. Which may be the point – the country is in upheaval and it makes sense that the corrupt regime of the looters would feature lots of backstabbing and power shifts. We need to get a sense of the huge number of people involved in the corrupt system and the speed with which they can fall out of favor.
But Mouch has staying power. He shows up at the very beginning and is here to stay. He's one of the three who tortures Galt at the end of the novel, along with fellow long-staying looters James and Ferris. He's also one of the only looters to get an actual backstory.
Mouch led an undistinguished life. He was a bad student and was bad with money. He started off his career working for an advertising agency that sold bogus cure-all medicines. Sounds like a real winner.
From then on, people helped Wesley Mouch to advance, for the same reason as that which had prompted Uncle Julius: they were people who believed that mediocrity was safe.... By the situation of the moment, they had concluded that Wesley Mouch was a man of superlative skill and cunning, since millions aspired to power, but he was the one who had achieved it. (188.8.131.52)
In this respect, he is representative of everyone who becomes a major player in the government, and it's no mistake that he runs the powerful Economic Planning Bureau. The mediocre Mouch gets into positions of great responsibility, where mediocrity itself becomes a very dangerous trait to possess.