Is it a deeply buried -- but struggling to get to the surface -- love of objective truth, hard reality, "binary" truth or falsehood, peeking through the fog in a world of subjective reality, anything goes, confusion, a thousand shades of gray in everything but no objective truth?

I think so.

When a word serves a useful purpose, it is quick to catch on. When a word is useless or counter to reality, it is not needed, and is not likely to catch on. For example, the various made-up gender pronouns for the 3rd through 19th "genders" (ze, zem, zir, etc.) People don't use them because they instinctively know they're not needed; they don't help express a reality they're trying to communicate. In the example of genders, it's because the "reality" of 19+ genders doesn't exist! So we don't need a way to communicate that a given individual belongs to one of those non-standard "genders".

So why has literally taken off like wildfire literally everywhere in the English speaking world? I think I'm on to something.

I think for so many people, the word means, "Really, actually, come on, I mean it, I'm not joking, it's true, true for everyone, objectively true" all at once.

So why has literally taken off like wildfire literally everywhere in the English speaking world?  I think I'm on to something.

I haven't noticed any increase in use of the adverb.  Its almost-always incorrect usage has long been annoying to me.  Its misuse seems ridiculously high among talk-radio hosts and sports announcers, e.g. [*]:

•  "Trump was literally on fire for his campaign speech last night!"
•  "Hillary was literally dead after her last campaign stop yesterday."
•  "The winning touchdown pass was literally a miracle!"[‡]
•  "The tight end literally killed the safety on that touchdown play!"

One might think they, of all people, would eventually learn its correct usage, because it's a professional issue of developing specific on-the-air skills: Saying what they mean, and meaning literally (ahem!) what they say.  But long ago, I conditioned my brain to detect the error then quickly stifle my exasperation, and resume listening.

I think for so many people, the word means, "Really, actually, come on, I mean it, I'm not joking, it's true, true for everyone, objectively true" all at once.

I disagree completely.  My conclusion, reached many years ago, is that the typical misuser believes that "literally" means "in literary wording",  which the speaker (or writer) does understand to be contrary to objective reality.  So to its typical misuser, the subject word mistakenly means means "figuratively",  and typically "metaphorically".

It's really an example of the increasing ignorance, by native speakers of English, of their own mother tongue [†].  Given that vanishingly few people in the U.S.A. take classes in Latin nowadays, the typical misuser would never have encountered "littera, -ae" (f.) as meaning a "letter of the alphabet" (e.g., per Cicero).  I'd hoped to find a derivative adverb nearly identical to "litteralis, -e   -is",  meaning "word-by-word", but that word is not attested until Late Latin.  The same meaning is provided for Classical Latin by the 2nd of 3 attested meanings for "litterātē" (English kept more-or-less only its 3rd meaning, which is translated as "learnedly"; the 1st meaning is translated as "legibly", in the sense of writing in well-formed letters).

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Note *: Ad hoc simulated quotes.  That confessed, I'd be really surprised if CathInfo readers who listen to radio or t.v. (especially those who indulge themselves with worldly coverage of specific sports) haven't heard nearly identical words from the mouths of radio hosts or sports announcers.

Note ‡: But wait!  Traditio Network insists that there are no more genuinely Catholic colleges (or universities) left in the U.S.A., so whose team could possibly have qualified nowadays to have been granted such a miracle?

Note †: Thus seemingly an excellent candidate for <https://www.cathinfo.com/fighting-errors-in-the-modern-world/>, altho' it's certainly the prerogative of the owner-moderator to disagree.