Complex sentence: Since his two year ban for testing positive in 2006, he has become clean, and returned to competition, which he attributes to his then 7-year old daughter for searching his name online and learning of his past troubles.
Split into simpler sentences: Since his two year ban for testing positive in 2006, he has become clean, and returned to competition. Which he contributes to his then 7-year old daughter for searching his name online and learning of his past troubles.