In specific, I thought that using を twice in the same sentence was forbidden but here it is used 「素晴らしいということを有名人を使って。。。」
→ You are correct and it is certainly forbidden to use を twice in a sentence. However, you can use one を per verb and a sentence can have more than one verb. It is because a sentence can have a main clause and subordinate clauses. In this case, "素晴らしいということを(object) 放送する(verb)" and "有名人を(object) 使う(verb)".
→ Furthermore, the media use celebrities and highly broadcast how wonderful the way of life which "chasing one's ideal self", and the bookstores are flooded with how-to books of "I have succeeded this way".
I hope my translation makes sense.