Exactly, but the general expectation of this campaign was 'to quickly take Paris, happy end'. Paris taken, enemy army destroyed in one blow.
But the German victory in Battle of the Marne means actually just taking more French territory. This doesn't mean the end of otherwise numerous and still strong French Army. The Germans are bogged around Verdun and their lines can only stretch so far without exposing their flanks.
Certainly the bloodshed nearby Paris would have been a with significant impact, but it might have taken one or two more blows against Joffre to force him to throw towel.
Would be Germans after victory at Marne still able in 1914 to deliver such blows? Or the growingly grimdark campaign would continue well at least to another year? Schlieffen Plan therefore fails in any case, because actually French themselves must decide it.
A German victory at the Marne was highly improbable and it's usure if it would have changed anything at all in the western front at that point. This was the strategical situation of the western front when the battle began:
The battle of the Marne saw the German I and II Armies (from west to east, led respectively by Alexander von Kluck and Karl von Bülow) being attacked and driven back by (from east to west) the French Ninth Army (commanded by Ferdinand Foch), the French Fifth Army (commanded by Louis Franchet d'Esperèy), the BEf (commanded by Sir John French) and the French Sixth Army (commanded by Michel-Joseph Maunoury) which was further supported by the Paris garrison under the command of general Joseph Galliéni.
Just a cursory look at the map will reveal the dificulty of the German situation: Moltke had ordered his right flank (the crucial part of the offensive force in the so-called Schlieffen Plan, the "hammer") to turn south-west and to march diagonally in front of Paris (which lay directly to the west of the German I Army right flank) believing that:
- Either Paris was not garrisoned or that its garrison would be too weak or unwilling to attack the German right flank.
- That all the French field armies were located to the south and southeast being engaged in combat with the remaining German armies and so that the German I Army would effectively be able to envelop their exposed left flank and either attack them in the flank and rearguard or force them to a general retreat all the way to the Jura and the Swiss border.
Neither of these two assumptions was true. Joffre had been able to shift forces from the center and east to his left flank, and he'd also been able to stop the British from retreating to the Channel ports after the battle of Mons. The garrison of Paris had been reinforced by the new Sixth Army (formed with colonial forces, reservists and some divisions moved by rail to Paris from the Third Army in Lorraine). In fact, by advancing directly south in front of Paris, Moltke, Kluck and Bülow were sticking their heads into a trap, because Kluck's right flank was wide open and exposed to attack.
Even if Kluck and Bülow had managed to cooperate without allowing a gap to open between their armies, and Kluck had repulsed the attacks of Maunoury's Sixth Army (which suffered massive losses attacking Kluck's army), there still remained the question that the French would have been able to retreat behind the massive ring of forts that surrounded Paris (and which, with a commander like Galliéni would have been probably defended vigorously), and behind the Seine, and that if the Germans followed they risked to be attacked by the French on their right flank again, unless they left strong forces screening Paris (and their increasingly longer and exposed right flank).
The original draft of the so-called Schlieffen Plan called for an envelopement of the French army with the German right wing walking along the Channel coast, and crossing the Seine to the northwest of Paris, downriver from the city. This needed many more troops than the Germans had either in 1905 or in 1914 (or that they would have been able to gather in any conceivable scenario)
