I am not qualified to argue the details with you.
But he charmed tens of millions, and if we include the world - hundreds of millions. It’s an accomplishment. Does he qualify as the most successful snake oil salesman?
Your point is well-taken.
But the most successful snake oil salesmen never repeated a location. The less successful were those who did make a second call on a town...and they often found themselves dressed in tar and feathers.
Obama's act isn't wearing well...