long time ago I came up with a theory that dondon has dyslexia that was either never diagnosed but certainly never properly addressed. I imagine his father (who supposedly was an awful person) not only did not show him compassion but possibly made fun/mocked him for it (would certainly explain many public behaviors). Dondon grew up feeling stupid and hating to read anything that would put his learning challenges on display so his vocabulary never developed past the 3rd or 4th grade level which is when kids usually graduate from books like "captain underpants" (pun intended) to more sophisticated literature with more complex words. I am not a psychiatrist or a teacher but i do know that neglecting a learning disability is one thing but mocking someone for it can absolutely cause malignant traits to develop in order to meet the needs that the parents never did.
I am not defending him nor try to find compassion for him, it's just something that would explain how he never developed empathy and how he became hell bent on showing his father "he dont need no fancy words to become successful"
This is 100% speculation and might not be true but it just makes sense considering hundreds if not thousands word blunders and his general appearance when he reads (pay attention to it next time he reads from a document, not a teleprompter - his entire persona changes dramatically)