Toffee is still a huge power crazed maniac with a vengeance.
His reasons are probably founded though. A diplomatic solution was probably impossible considering the Butterfly's high comfort of the status quo.
If nothing else though, Toffee shook up the Butterfly kingdom from it's status quo and now they'll have to listen to the monsters.
It's going to be the Avarius family and monsters like Buff Frog who are going to pick up the pieces of the wreckage Toffee will leave when he inevitably loses.
Buff Frog is more or less an ally of Star Butterfly and the Avarius family has show to at least have peaceful relations with the Butterfly family, save Ludo who was just as power hungry as Toffee.
So they have a chance of convincing the Butterfly family to give the monsters a chance once this tragedy blows over.
Both Ludo and Toffee are instigators and sometimes you really need them to shake up the powers at be to cause them to re-think their position. He's doing good work, however brutally.