Complex sentence: In 2002, Megadeth was temporarily disbanded because of Mustaine's arm injury, but the band re-established in 2004, performing without bassist David Ellefson because he had taken legal action against Dave Mustaine.
Split into simpler sentences: In 2002, Megadeth was temporarily disbanded because of Mustaine's arm injury. The band was re-established in 2004 without bassist David Ellefson, who took legal action against Dave Mustaine.