Well, line producing essentially consists of the day-to-day production needs, as well as making sure everything stays on budget, or at least as close as possible. Staying on budget is extremely essential because the film industry is a business when it comes down to it, and there can only be so much money thrown into a particular film. If you're going crazy with money spent on a film then you start to lose the profit and the producer(s) are not going to be happy. 

﻿The Wachowski siblings started their careers out successfully with a few big hits, including The Matrix, until they found themselves in a rut. A $200 million TV show remake failed, as well as a $140 million independent film, so they needed a big hit. 

Daniel Myrick and Eduardo Sanchez wrote a loose script, hired some super low-budget actors, and let them improv their way through the film, and somehow it grossed almost $300 million. I say somehow because obviously they didn't have class A actors or great effects, or really anything of that sort. It was something new and innovative, and pretty much started a new genre, which is why it was as successful as it turned out.

He made the decision to make fun of himself through film, starting with a bit part in Tropic Thunder as Les Grossman. For him to get another big role, he first had to laugh at himself.