So it seems they struck while the enemy is in the middle of setting up an operation against them. The cave full of criminals was being readied for killing work. The count Faltoria was also feeding the feudal lord Foronda false information in order to throw off his efforts against the organization.
This means their own operation to destroy the organization couldn't have come at a better time: any later and the organization might have struck first with its den of killers awaiting the opportunity to attack, and the count orchestrating the assassination of the feudal lord.
Why would they branch out to political assassination from child trafficking? It's because they likely want to secure the future of the organization by taking political power. If the have a feudal lord backing them, they'll become near impossible to take down, and then their evil business can continue unopposed.