Rosecrans had been in communication with Hooker. Because Hooker didn't feel he was able to move when Rosecrans wanted him to the carrying out of the plan was delayed until after Rosecrans' removal. Grant's presence had nothing to do with the design or carrying out of the plan.
A letter written by William le Duc who piloted the first boat that carried supplies to Chattanooga after the opening of the Cracker Line to Gen Richard Johnson:
Hastings, July 6, 1886.
My Dear General Johnson:
The proof-sheet received and read. Please accept my thanks for your kindly mention, but you give me credit overmuch. If not beyond your control, could you not have the text changed, so as to express the exact truth, which was that I found a scow in process of construction on the banks of the Tennessee River when I arrived there with General Hooker's command, which, as you of course know, was sent from the Army of the Potomac to the assistance of Rosecrans? Our first duty being to secure the long line of communication between Nashville and Chattanooga, and to do whatever might be done to forward supplies to the famishing army at Chattanooga, Rosecrans, with prudent forethought, had ordered the construction of five steamers on the Tennessee, and the repair of the railroad, two very important bridges of which had been destroyed by the rebels, one across the Tennessee and one over the Rolling Stone, half-way between Bridgeport and Chattanooga. One of these flat-bottomed steam scows had been put on some posts and blocking near the bank of the river, and the work was prosecuted by a very competent ship-carpenter by the name of Turner, who was employed by Captain Edwards, A.Q.M. The timbers and lumber for the boats had to be made from the stump, and it was with difficulty that the machinery was shipped over the railroad from Nashville, as every engine and car was needed to transport rations. When the rains and rebel cavalry had made the wagon-road on the north side of the river impassable, rapid building of the steamboat became ofthe highest importance. I took personal supervision of the work, and crowded it forward night as well as day, saving the hull from destruction by floating it upon pontoons, and navigated it, as you describe, to Kelly's Ferry, with the first cargo of rations to reach the starving army. But for my action it is quite safe to say this boat would not have been launched for some weeks after it was, if at all, and certainly could not have contributed, as it did materially, to the success of our efforts to secure possession of that very important strategic position, Chattanooga.
General Rosecrans has not received the credit due him for his skilful conduct of the campaign. He foresaw the probable need of river transportation, and, so far as giving orders, provided for the emergency. Had those intrusted with the execution of these orders pushed through their work more energetically, and had the boats ready for use when needed, great loss of animals and distress of men would have been saved, and Rosecrans would have retained his position as commander of the Army of the Cumberland. The unfriendliness of Assistant Secretary Dana and the impatience of Secretary Stanton secured his downfall.
Respectfully, etc.,
Wm. G. Le Duc.
page 419
https://books.google.com/books?dq=r...&id=X9FBAAAAIAAJ#v=onepage&q=overmuch&f=false