They were led by Kavil, who was tempted by the possibility of social elevation in the Empire through his duties.
After being driven off of Eiattu 6, Moff Leonia Tavira joined with Kavil's Corsairs. She intended to overthrow Kavil with support from the New Republic, and to this end kidnapped Tycho Celchu and "Leia Organa." Presumably the Corsairs later became part of her Invids organization.