When you put together deep knowledge about a subject that intensely matters to you, charisma happens. You gain courage to share your passion, and when you do that, folks follow.
~ Jerry Porras
The essential difference with Builders is that they've found something to do that matters to them and are therefore so passionately engaged, they rise above the personality baggage that would otherwise hold them down. Whatever they are doing has so much meaning to them that the cause itself provides charisma and they plug into it as if it was electrical current.