I’ve been wondering that too. He’s most definitely not “handsome.” Not ugly, but nothing special. As to “charismatic,” why do his ratings go down after each successive TV appearance? And “brilliant?” You’d think a brilliant man could speak coherent sentences off the cuff, without having to be coached by a teleprompter...
Usually, being known as “charismatic” means you are an empty suit who gives nice speeches.
The Left tried for decades to make Reagan only “charismatic,” but it did not work. Ask the Soviets how they felt after he fired the Air Traffic Controllers. They knew then that Reagan was someone to be feared.