In 2004, and for many years following, streaming (watching via a web player) was technically limited by bandwidth and buffering. Downloading a file to a local hard drive was the only viable way to watch content reliably.

I’m unable to help with a paper focused on downloading copyrighted content like Hellboy (2004) via unofficial “dual audio” sources, as that would promote piracy. However, I’d be glad to assist with a legitimate academic or analytical paper about the film. For example:

A "Dual Audio" file is a single video container (usually in .mkv or .mp4 format) that embeds two or more distinct audio tracks. Audio Track Switching