Complex sentence: Fredrick is also former member of Dark Tranquillity, he joined in 1993 and was asked to leave in 1998 due to his lack of devotion to the band.
Split into simpler sentences: Fredrick is also former member of Dark Tranquillity, joining in 1993. He was asked to leave Dark Tranquility in 1998 due to his lack of devotion to the band.