Complex sentence: He failed to progress to the "Boys" category at the "judges' houses", but after guest judge Nicole Scherzinger suggested that Niall joined One Direction, with Harry Styles, Zayn Malik, Liam Payne and Louis Tomlinson, the group became a reality.
Split into simpler sentences: He failed to progress to the "Boys" category at the "judges' houses". After guest judge Nicole Scherzinger suggested that Niall joined One Direction, with Harry Styles, Zayn Malik, Liam Payne and Louis Tomlinson, the group became a reality.