Depends on how it's used.

"Not many people read the whole thing because HN."

Now, you could add the "of" and just leave it at that, and take it literally. But the implication is so much more than just saying "because of HN."

"People are so fat here because 'merica."

You're exactly right. This is just leaving out the "of". The article interprets this to mean that the word "because" has become a new preposition used in place of the proposition "of". Another interpretation is that "because" retains its grammatical usage but a new sentence structure has become acceptable. I personally interpret it the second way. Each domain has its own grammatical structure.

Even "because of short attention spans" is leaving out information... which (or whose) attention spans are we talking about. There is a qualifier or article missing somewhere. A "his", "their", "some" or something.

As I said in another comment, to me it implies the subject is dumb or hasty or something. As in a little bit of caveman speak maybe ("He hit own head because stupid").

That's one aspect to it. The article summarizes it well at the end:

> "It means something like 'I'm so busy being totally absorbed by X that I don’t need to explain further, and you should know about this because it's a completely valid incredibly important thing to be doing'"

Because brevity and wit.

That's pretty much it. The linguists just gave it a fancy technical name.

I wouldn't worry too much - this is just a fad.

People get bored and do weird things.

no, there is more. Take "because yay!". Doesn't necessarily make sense if you put an "of" in there. Yet there is something in common between "because yay!" and "because math" that is not there between "because yay!" and "because of math".