Shrinking a standard two-hour film down to 300MB without causing severe pixelation requires advanced video encoding technologies. The phenomenon relies heavily on two primary factors:

When attempting to click a "Download" link on these sites, users are rarely given the file immediately. Instead, they are subjected to a gauntlet of redirect loops, hidden click-jackers, and aggressive pop-under ads. These ads frequently deploy tactics, attempting to force-download malicious software onto the user’s device under the guise of "required video codecs" or "system updates." The Danger of Fake Extensions

H.265 offers up to 50% better data compression than H.264 at the same level of video quality.

For a phone screen (5 to 6 inches), it looks "fine." For a 55-inch TV, it looks like a mosaic.