1812 was not silly and it only occurred on the singular order of N.
Invasion of Silesia was a singular order by Frederick II, was he enlightened king blessed by divine grace, or a bloodthirsty dictator ?
War against France in 1805 was a singular decision of Alexandre I (see E.Sokolov, Austerlitz), was he little father of his peoples or a parricid usurpator ?
War against France in 1756 started by the capture in peace time of french merchant ships, by order of King Georges, was he a Gracious King or a trustless pirate ?
and so on...
Napoleon used to the full the institutions he inherited or created, and had ultimate decision on peace and war. But this was the case of any crowned head of the period, including UK.