Sidious did not run the day-to-day affairs of the war. I have no idea where you got that from. Sidious twisted certain events for his purpose (because the Clone Wars was his war), but he didn't tell Grievous what planet to attack unless it was absolutely vital to the Plan.
Its canon , I thought you were the great Canon keeper ?
Sidious made all the plans , made sure all the attacks by Grievous were not complete waste of time .
Grievous was the Face of the Battles , but he was just a commander doing what he was told PERIOD .
Before he was a Cyborg he was doing what he did in the movies , make attacks and run when they were losing . He almost died from it or did you forget that ?
He was not some Great General and when he was not needed no longer Anakin would have killed him like the rest !
And Grievous was a great general. He may have been a tool, but a useful one. Sidious had faith in Grievous' abilities, that's kinda the reason Sidious had Dooku orchestrate Grievous' 'accident.'