Non-functional components, like multiplayer files that won't work on official servers anyway, are frequently deleted. The Pros and Cons of Using Repacks
Repackers like BlackBox use several "ripping" and recoding techniques to achieve such small sizes: Language Removal: blackbox games repack
was a prominent "scene" group known for creating these installers. Unlike standard "lossless" repacks, groups like BlackBox sometimes used "lossy" methods to achieve extreme file sizes, such as: blackbox games repack