Complex sentence: Despite Wilson's pledge to record an even superior follow-up, entitled "Bambu", his continuing decline into substance abuse and personal problems ensured that the album remained unfinished at the time of Wilson's drowning death in December 1983.
Split into simpler sentences: Despite Wilson's intended to record an even superior follow-up, entitled "Bambu". But his continuing decline into substance abuse and personal problems ensured that the album remained unfinished at the time of Wilson's drowning death in December 1983.