Neutron (Quantum 6)

[Michele]

I think it's a two-party job. There is one party that is a superpower on this world, which stood to gain from the destruction of the Frankish, and an outside player having its own reasons to curb that power. The outsider provided the know-how, the local player carried out the plan.
I don't know who the outsider is; one would need to look into what Frankish policies were a threat for someone out there. As to the local power, it must be the British Empire; not very affected by the explosions, but greatly benefiting from the disappearance of a European hegemonic power.