That perception exists with Urth, for some reasons:
1) Asymmetrical threat projection
In the case of war, Urth's diplomatic ability is portrayed as being extremely potent and dangerous, to the point of being capable of triggering revolutions and manipulate nations to go to war on his behalf.
In the case of peace, you described Urth intentions as good and benevolent, with the diplomacy thing not really showing up as a threat (as opposed to a more realistic view where peace could be an avenue for further infiltration, and more of Urth's sneak attacks, blessing stealing and evilness).
2) Perceived punishment for picking the wrong decision
You described the Caradysh (OOC) as being a peer power.
But the experience of the last turn has pretty much shown that they're not. They have many more actions, more heroes, and more necromancy related boons than the Arthwyd do. This is interpreted as a bait and switch, a punishment for picking the option than the GM disliked.
3) Openly stating your preference for one option.
Having a motive makes making the accusation easier.
4) Action escalation and lock-in
While you can argue that it's your GM prerogative, going from deciding to continuing the war to having Urth massively escalate by triggering not only a revolution, but also immediately a war between us and a major lowland power, during which we have absolutely zero power to intervene, is interpreted as railroading.
Unfortunately, in this case you failed to sufficiently signal how dangerous everything, and so we're now in a methaphorical trainwreck.