Mono, ON (Adam Jones) Suneel Gupta gives several examples of well-known people who succeeded at getting heard without the classic public speaking charm in his new book Backable. While Fred Rogers was testifying before Congress and saving funding for public tv, he talked in a monotone and fumbled around with papers. Ken Robinson slouches with his hand in his pocket when he gives the most-watched TED Talk of all time. Both Steve Jobs and Elon Musk launched big products with speeches that completely ignored presentation basics.
As Gupta points out, conviction is a much bigger deal than technique. “When people earnestly believe in what they’re saying, they’ll simply let their conviction show through whatever style feels most natural.” He adds: “You’re much better off walking into a room with low production values than the other way around.”
I’ve found that a strong conviction proves one’s commitment to a cause or principle. Even if the appeal benefits the persuader personally, they let you know something big is up.