Cicero on the primary goal of oratory:
"As, therefore, the two principal qualities required in an Orator, are to be neat and clear in stating the nature of his subject, and warm and forcible in moving the passions; and as he who fires and inflames his audience, will always effect more than he who can barely inform and amuse them..."
Cicero describes the problem the OP reports:
"But let us return to Calvus whom we have just mentioned,—an Orator who had received more literary improvements than Curio, and had a more accurate and delicate manner of speaking, which he conducted with great taste and elegance; but, (by being too minute and nice a critic upon himself,) while he was labouring to correct and refine his language, he suffered all the force and spirit of it to evaporate. In short, it was so exquisitely polished, as to charm the eye of every skilful observer; but it was little noticed by the common people in a crowded Forum, which is the proper theatre of Eloquence."
Nuanced communication not working at scale, 2100 years ago.
[1] https://www.gutenberg.org/cache/epub/9776/pg9776-images.html
Nuance requires representing uncertainty and is higher complexity from accounting for multiple special cases. Placing more cognitive load and attentional demands on receiver.
Human communication is lossy and decoding can be non-trivial inference. Given that everyone comes with differing priors, the more finer grained and complex details are required in reconstructing message intent, the more likely it is to be misconstruected. Failing to attend to a single core detail can rend meaning.
At scale the chance for errors to propagate without correction increases.
Getting rid of fine grained details and communicating a lower entropy message inline with a crowd's biases also ensures it's more likely to survive in a form close to original intent. A good manipulative orator focuses less on truth or content and more on minimizing mismatch between receiver mental states and orator's directional preferences.