Hence Charles I’s reluctance to sign off on the (almost certainly unjust) Bill of Attainder on Strafford. Only when it was clear that revolution was the alternative did the King betray his faithful minister.
Indeed, the mob was at the gates. And London mobs were no joke ( same with Parisian or Neapolitan mobs ); whilst no-one felt he did it because of his own safety, his wife, children and line of succession were trapped. And as you say, he wanted to avoid war.
Whatever his remorse, in retrospect it was the right decision. I hope I would do the same: probably even Bismarck would. Sometimes the brutal decision to sacrifice the innocent to save the maximum, as in lifeboat situations, is the only unemotional option.