As for the impact of Bagration/Cobra, well, the catastrophic German defeats did actually not come as much of a surprise to those among the General Staff, precious few as they were, who had realised the poor state of the contemporary Wehrmacht which had for all intents and purposes reverted to a pre-modern force with its limited degree of motorisation, shaky fuel supply, etc. - aka "der Krieg des armen Mannes", the "poor mans war", and that on top of being utterly outnumbered and outgunned, attempting to defend divisonal frontages of up to 30 kms with very depleted formations, which of course was a quite farcical undertaking... HG Mitte prior to Bagration was a rotten edifice if there ever was one.
But it was always largely an unmotorised force.
Yes there are mobile formations, trucks and air supply
But the Germans never had enough trucks to have them for anything like all the army, nor would have had enough fuel to run them had they had.
Their attempts at air supply (Demyansk, Stalingrad, Tunisia) were only even attemptable by cannibalising the Luftwaffe's own training programmes
The vast bulk of their army marched on foot, with guns and supplies drawn by horses and reliant on railheads.
The motorised forces they did have were a bewildering and non-standard variety of mostly civilian trucks impressed or looted that were not suited to hard military use and hard to keep repaired.