The 5.1 channel was a flex. It meant the rip was untouched from the Blu-ray source. Most pirates would downmix this to stereo via VLC player, losing the director’s intent entirely. But the file didn't care. The file was pure. BluRip is the verb. This wasn't a web-dl or a screener. Someone bought the physical Blu-ray disc (or rented it from Blockbuster during its death rattle), put it in a PC drive, and used software (likely MakeMKV or HandBrake) to strip the encryption and compress the massive 25GB Blu-ray stream into something you could download over a weekend.
This process took hours. The ripper had to calibrate the bitrate. Too high, and the file is huge and nobody seeds it. Too low, and the pixels turn into soup during the casino scene. BluRip signifies a "scene standard"—a specific set of encoding rules that ensured quality. Finally, we reach the most haunting part: FLY635 . What.Happens.in.Vegas.2008.1080p.5.1.BluRip.FLY635
Blu-ray had won the format war against HD-DVD only months earlier (February 2008). Most people were still watching DVDs (480p) on CRT televisions. A 1080p file was enormous—typically 8GB to 12GB. For a rom-com. On a 500GB hard drive. But the file didn't care