Each of the parts has slightly different origins:
Quickscoping is a tactic used in shooters where you zoom in with a sniper rifle but shoot before the graphics actually show where you are zoomed. Certain games gave you an accuracy boost as soon as you started zoom regardless of when the animation actually showed you zoomed in. Extremely fast quickscopes just look like you shooting the gun without scoping at all.
The 360 part comes from people turning their aiming sensitivity up and spinning around in a circle before shooting. It is just trick shooting in video games.
There are a series of words that people like to chain together that all contain an "8" sound in them:
gr8 b8 m8 i r8 8/8
It's a very specific variation on textese that intentionally takes it as far as it can be taken.
MLG is Major League Gaming which is one of the larger eSports leagues. People like to claim they are MLG players because they think it gives them some sort of credibility.
YOLO is You Only Live Once and it was a big tag on social media sites for awhile. Swag somehow became associated with it and now you see yoloswag.
Both 420 and "blaze it" are references to smoking weed. A lot of kids who posted videos showing off their self-proclaimed MLG level skillz had names like "XXX420blazeitXXX" and it became a quick target when the parodies starting showing up.
The Illuminati is just a classic conspiracy theory and it gets trotted out whenever people are making fun of conspiracy theorists. Illuminati Confirmed references a specific group of parodies of the issue.
So the reason you might see all of these near each other now is that people are chaining jokes that were only somewhat related in as a meta-joke on the whole subject. There is no particular reason this group of jokes is seen together other than:
Hope that helps.