Complex sentence: Oliver helped Toulon win the Pro D2 title and earn automatic promotion to the following season's Top 14 and then decided to leave Toulon after only one year and announced his retirement from professional rugby and went to the University of Oxford to study a postgraduate degree.
Split into simpler sentences: Oliver helped Toulon win the Pro D2 title and earn automatic promotion to the following season's Top 14. He then decided to leave Toulon after only one year and announced his retirement from professional rugby, heading to the University of Oxford to study for a postgraduate degree.