From what I heard, ML got involved in a scheme to usurp the line of succession and place someone else on the throne, this would involve FL's nephew being killed since her dead sister's son is the crown prince. ML wasn't interested at first since the prince is his wife's nephew but when FL was running from reality and he was bitter he ended up involved. To not have FL and son dragged down by this shit show he got involved in after ML and FL some what made up, they divorced. Failing to usurp the throne would mean all his property taken, title stripped and the family punished but since FL and son left and gave up the Bernhardt name would be fine since they were not part of the family anymore. FL also ends up inheriting her brother's title after he suddenly got sick and died and his son being too young to inherit, him having named her his successor.