Good question.
Probably because the press made sure that the "useful idiots" did NOT learn the following..
0bama’s father was a communist.
His step-father was a communist.
His mother was a communist “fellow traveller” who met his father when they were both studying Russian, the language that radical lefties studied in the 60's.
His mentor, Frank Marshall Davis, was a communist who was under FBI Surveillance.
His close buddy of twenty seven years (yes, they met in 1982) Bill Ayers is a communist.
He sought out Marxist Professors in college (his words) and found them - Edward Said, former PLO spokesman, and close friend of 0bama AND Ayers from 1982.
His hero, and author of his playbook, Saul Alinsky, was a communist.
His friend Mike Klonsky is a communist.
His friend, and current Palestinian Authority spokesman, Rashid Khalidi, is a communist.
His Preacher of 20 years preaches Black Liberation Theology, a Marxist ideology.