While Cao Cao was skillful - he was also insanely lucky. Many of his battles (military or political) were won where he quickly captialized on events that were not within his control (enemy disorganized, lucky break throughs, rival deciding not to take action, etc) and he probably has more brushes with death compared to most of the other characters. Even Cao Cao realized this, which is why he turned superstitous in his latter years.
One of his crowning moments of glory, the Battle of White Wolf Mountain was won due to sheer luck. His force was not spotted by Wuhuan scouts until he was practically atop them, and he then proceeded to defeat his unprepared enemy which numbered between 100,000 to 300,000 Wuhuan and Chinese refugees with only his cavalry (unknown number but impossible to be more than 50,000, very likely much less) which had just forced march 200+ km. 200,000 surrendered to him (this includes non combatants however).
After winning the battle, realizing how lucky he had been, he went back to the capital and promoted everyone who had told him how stupid it would be to try such a thing.