I think it's the degree of bullshit that increases gradually. To speak from experience, when you are a grad student you get a feeling like there's corruption but overall your project seems like it's important and making a real contribution (hopefully). You also don't have to worry about where the money is coming from. Sometimes the grant as a whole is total bullshit but there is enough discretionary spending included that great science comes out of it. But you don't realize this until you're writing grants, and by then you're maybe too deep in the game to pull out. Essentially, you end up becoming a manager once you get tenure. There is no epiphany; it's more like a slow creep.