Owning a faster video card and editing configuration files to cheat the game's systems. This stuff requires an .ini edit, it's not just having a faster card.
Edit: I'll provide a caveat that the .ini edits SHOULD be relatively benign, outside of this. I understand why people would have a reason to make them. I'm just saying either plug the hole, or check the .ini and lock down those settings if you can't.
Also, the one really ugly video in the link there is actually on Fallout 4's engine, there's been no clear video evidence backing that kind of attack speed increase on 76 that I've seen, after poking around.