That was an example of prewar theory running up against real-world testing. It turned out that one raid was not enough knock out a target; rather, it had to be hit, repeatedly, to keep it out of action. Everyone pretty much underestimated the degree to which industrial facilities could be brought back into operation by a large, industrialized nation-state. And to keep hitting targets in that fashion required a larger bomber force than most anticipated. The Allies were also led astray by bomb damage assessment — recon photos from 30,000 feet looked impressive, showing a bomb-scarred landscape. Only at ground level, the damage was frequently far less than such high-altitude photos implied.
Nevertheless, the Oil and Transportation Plans proved highly detrimental to the Germany war economy — its armaments production index peaked in July 1944 and fell off rapidly after that. Bomber Command's effort against the Ruhr in 1943 also had a big impact, effectively flat-lining German production for about seven months. (Adam Tooze covers this in his book The Wages of Destruction: The Making and Breaking of the Nazi Economy.)
Moreover, there were critical target types not attacked, e.g. the German electrical supply. A sustained campaign against that could have had a huge impact. But for various reasons it was left off the target lists.