Well, at those times, when the Marishiten cult was important to warriors, winning at war was the bushi job*. When mantaining peace became their role, Marishiten cult went down.
So I think the traits cultivated via Marishiten cult had not much to do with preserving peace but with prevailing in the battlefield.
*As Asakura Norikage said: "Call the warrior a dog. call him a beast: winning is his business"
Hmmm. I would say that the job of the bushi was both to win wars AND maintain the peace, and it was the environment that changed with the coming of the Edo period, to one of far more structure and solidity. So the challenges that the warrior faced became different and perhaps he had less of a need for his will to be invisible and unbound by the will of his opponents.
I think the question of why Marishiten worship declined after Tokugawa is an interesting one, but I also think it is interesting to look at how prevalent it was at it peak, I don't think her cult was ever universal among the warrior class.