I just don't think it's a simple as a yes or no answer. You might as well say "Sulla caused the fall of Rome" - as he was the first to march on Rome and take power by force.
There were many other examples for corrupt Governors prior to Caesar, indeed, prior to his consulship Caesar prosecuted some of them.
IMHO, this would have been the opinion of your namesake and his string pullers in the Senate, but in fact the conquest of Gaul provided income, troops, senators and citizens for hundreds of years of Empire following conquest. The republic was already dead, the Senate just didn't know it. Italy itself was not threatened again by Gallic (they were now citizens) or Germanic (they were faced by Legions in Gaul or Pannonia) tribespeople again for at least 200 years after the Gallic wars - thankyou Caesar !
He did further the Italicization of Gaul, and Gaul populated by his clients and citizens offered exactly that - a buffer and a source of great wealth.
My own opinion is that those elements in the Senate that wished to prosecute Caesar on his return to private citizen status, were so incapable of compromise, and so hapless in their final actions, (Thinking once again of your namesake) that they left Caesar no option. Lay down you legions and return to Rome so we can strip you of your estates and banish you and deny you fire and water.....or....you have 7 veteran legions at your command......and the people of Rome.....love you.....I know what I'd do !