Maybe because he didn't try and it wasn't real fight? Yet they beat fighters who look like they had boxing training.
I think the way the fantasy has to work is: Corbett darts around the ring while Jennings cluelessly stalks him hoping to nail him with a single lead power punch at a time. Meanwhile, Corbett uses his superhuman speed and reflexes to pot shot Jennings to death and escape to safety before the slow, low-IQ modern scrub can lay a glove on him. His size, reach, and power advantages would be completely worthless.
I rate Corbett very low for someone who was lineal champ. Personally i think some people are underrating him here, if he can stay away from the power of Fitzsimmons and Jeffries then i think he could hold his own against Jennings, who was NEVER anything impressive then again they wouldnt have the workrate and explosiveness of Jennings due to the long rounds, Jennings would try to take him out early Personally ill take Corbett by tight UD. Really moreso a reflection of how lowly i regard Jennings than how highly i regard Corbett
I love how unskilled and one dimentional fighters like Wilder or Ruddock have fair success in modern era, yet someone like Baer would lose to Butterbean.