Words like insincere, over-earnest, do not do justice to the type of word I need. Example sentence: The president of the company read his well crafted speech but it fell flat because of his obvious “———“.
Pretentious is the first word that grabs me. (Please use the noun form, pretentiousness, to fill in the blank. )
attempting to impress by affecting greater importance, talent, culture, etc., than is actually possessed.
affected, ostentatious, showy; overambitious, pompous, artificial, inflated, overblown, high-sounding, flowery, grandiose, elaborate, extravagant, flamboyant, ornate, grandiloquent, magniloquent, sophomoric;
Will pomposity fit?
adj. 1. Characterized by excessive self-esteem or exaggerated dignity; pretentious: pompous officials who enjoy giving orders.
American Heritage Dictionary
n, pl -ties
1. vain or ostentatious display of dignity or importance
Collins English Dictionary
1.Affectedly grand, solemn, or self-important.
Oxford Living Dictionary
1 : excessively elevated or ornate pompous rhetoric
2 : having or exhibiting self-importance : arrogant
"a pompous politician"
Not sure whether this word fits your intention of "gravitas", but it does mean possible affectation with the definitions containing descriptive words such as "pretentious" and "ostentatious".
The president of the company read his well crafted speech but it fell flat because of his obvious "pomposity".
affected behavior is not natural but is done to impress other people
His affected manner annoyed her.
marked by or given to speech or writing that is given exaggerated importance by artificial or empty means : marked by or given to bombast (pretentious inflated speech or writing )
the bombastic pronouncements of so many politicians
trying to seem very serious and important, in order to impress people
pompously or portentously overblown
This would best fit as a description of the speech itself, but my (former) favorite word might meet your needs:
Noun: a lofty, extravagantly colorful, pompous, or bombastic style, manner, or quality especially in language
The president of the company read his well crafted speech but it fell flat because of his obvious delusions of grandeur.
to give sufficient levity to the negative ending is made more difficult by the inclusion of "well-crafted". So we must attacked the nature of the delivery. A "well-crafted" speech would never appear insincere, but a delivery with an air of fakeness would qualify for fake gravitas. "Without the standing to deliver such sentiment".
Many ways to drive home what you mean, but to use a single word makes it difficult.
Perhaps not quite as near to the mark as some of the other suggestions, but nonetheless worth thinking about in this context is:
For me (I'm 54 and Australian, with the age and region understanding of English thus implied that should be taken into account), this word's meaning also bears more than a whiff of the idea of insincerity, although, strictly speaking, priggishness can be unconscious, especially as a result of one's upbringing. However, the same can likely also be said of "pompous". Only "pretentious" unambiguously conveys to me the idea of conscious deceit by the speaker about their own supposedly superior level of knowledge or worthiness.
Nonetheless, most of the suggestions are often used in a somewhat satirical or ironic context, so then things like "pompous" become more unambiguous. In that case, a word / phrase that I sometimes hear, particularly from the pens (or computers) of the better sardonic political commentators is:
with similar meaning to exalted, but the metaphor in this word's origin of having one's head in the air ("loft") or above the clouds is probably what gives it its usually ironic flavor. However, again, satire has to be clear in the other words you use around it. An older person may use the word for "exalted" in a genuinely admiring way, to express belief in the "height" (significance) of someone or their ideas.
Here's another one I don't hear much but would definitely convey the idea to me:
since the Defendant in Gilbert and Sullivan's "Trial by Jury" is described as having a "Supercilous Smile" (actually a description given to himself, speaking of himself in the third person in the Defendant's solo "Oh, gentlemen, listen, I pray"). The word's origin "supercilium" meaning "eyebrow", referring to the arrogant facial expression of a raised eyebrow at whatever the Defendant thought beneath him, also gives the word a particularly visual irony for me.
A warning on Portentous. I actually had to look this one up, because I have quite a different understanding of this word. Perhaps this is a reason not to use it (because if I misunderstand it, then maybe another native English speaker may not either). I read this word literally, meaning "filled with portent". But I don't believe I have EVER seen this word written outside Shakespeare (who rather liked it, using in the sense I understand it) other than by someone like Emily Bronte and the only time I believe I have ever heard it spoken (or sung) was by Kate Bush in her song "Moving" from "The Kick Inside". As explained in the Wikipedia article, the song is a tribute to Bush's dance teacher Lindsay Kemp, and unambiguously expresses Bush's supreme admiration for Kemp and her belief that Kemp was indeed filled with portent. The words are "... if your beauty is portentous" and, naturally for Kate Bush, spelt and pronounced "-tus" in the Shakespearean way rather than "-shus" as in "portentious" in the other answers. I suspect that many other people of my generation were taught the word by Kate Bush, and would therefore read it very differently from how you would like it read.
May not be an adjective or fit your example sentence but, in case it helps, one may call someone who displays fake gravitas a "tryhard".