Complex sentence: In 1991 Bonne became involved in a side project, Wasteland, which soon became more important for him than A Split-Second, which split up with Ickx continuing it as a solo project.
Split into simpler sentences: In 1991 Bonne became involved in a side project, Wasteland, which soon became more important for him than A Split-Second. The duo split up, with Ickx continuing A Split-Second as a solo project.