Jones ducked.
Ngannou wanted the Jones fight all along but he was unhappy with his contract and thought he could get a better deal elsewhere. Turned out he was right. Like the majority of fans he believed he had acquired the skills to stuff Jones TD's and would knock him out. He also wasn't afraid to take a loss as he already has a couple so it wouldn't be the end of the world.
Jones on the other hand is terrified of losing because remaining undefeated is a big part of his claim as the GOAT. He only committed to HW after Big Frank left. He's there to take advantage of a couple of favorable matchups, harvest the glory, and then ditch the sport before he has to fight Aspinall or Pavlovich.