Why is it common for people to default to a single causal source to explain new phenomena? I am constantly bombarded by allegations that almost every relatively unusual event is the result/proof of some conspiracy/plan set by a specific powerful entity.

The typical reasoning behind such claims follows:

"X happened because there is Y beneath it, and this event is the very proof of this fact!"

Here are some examples:


" Homosexual marriages are quite common today, because armageddon is
approaching!" " 
" Our country can't develop further, because USA,
China and other developed countries are afraid of us!" 
" 9/11! Whom else might have done this? of course the Saddam/Usama Bin
Laden/Iran/Pakistan/etc!" 
" Oh Have you recognized the verses  on this song when you play it backwards? This is the     proof of Satanists!"
" Oh look at these cards published in 1995. This is the exact
life we are living in today. Damn you illuminati!" 
" Omg I can see it, Here is the proof that Jesus was real. How else a face would
appear on a toast? What is that you are holding? A Tortilla. May
I look at that a bit closer? Ohhh, again!"


What is the name of this attitude of over-reductionism everything to some specific thing? A cognitive bias? Defense Mechanism? Straw man? Reduction ad Absurdum? Even maybe Chewbacca Defense [ This question encompasses the title of the question as well.]

Secondly, is there any term for "that specific thing" people reduces everything to? I want to be able to say "you associates everything to illuminati, because illuminati is your X" What term may I use here for X?

UPDATE: Other question of mine sounds related to this one. If you are intrigued by this question, check that one as well: Why are people inclined to praise or fear the unknown?
I don't quite know an agreed upon word for this type of thing, but I do know what you're talking about. 

At a very basic level, we use previous beliefs to interpret new information. In a way, it's at the core of how we perceive at all. I don't necessarily see these types of fallacious thinking as exceptions. Their belief about the order of the world is different, and so they interpret individual events differently. The examples you listed seem like instances of this happening. 

If anything, it's just simplistic thinking, or a tendency to over-synthesize information. Illuminati type conspirators need to bring a bunch of disparate information into a model that makes sense, so they form connections between things that don't really connect. It probably doesn't help that they expose themselves to a lot of information presented in a way that strongly suggests some sort of Illuminati presence.

But don't forget that we do the same thing. Many times, the difference is that those around us also agree with the assumptions we make, so we don't even notice.