1st. The following January, Marlon Jackson also announced he was leaving the group to pursue a solo career. In 1989, five years after their last album, the remaining quartet of Jackie, Tito, Jermaine and Randy released 2300 Jackson Street, which performed badly on the charts.
He quit the Jackson 5 to pursue a solo career instead of working with a Group.
and he went solo because joe jackson was trying to cut his creativity and Michael wanted freedom and he wanted to have his own freedom to write his own music and free to be creative on his own