You left out the best parts after that.

far back in prehistory, when the first primeval Vogons crawled out of the sea, evolution gave up on them. Through sheer obstinacy, though, the Vogons survived (partly by adapting a misplaced, badly malformed, and dyspeptic liver into a brain). As the radio show says: "What nature refused to give to them, they did without. Until their myriad anatomical deficiencies could be rectified with surgery." They then emigrated en masse to the MeagaBrantis star cluster (although the film has them staying on Vogsphere), the political hub of the galaxy. They banish the ruling philosophers to the tax office to lick stamps and within a few short Voge years took over pretty much all of the galactic civil service, where they form most of the Galactic bureaucracy