Hai Yuchen didn't believe in any 'Lifespan Display Mirror' or 'Fasting Pills'. He was too lazy to argue with his family who seemed to have been brainwashed. He pretended to believe them and asked them to call him when Song Juyao reappeared. After confirming his grandfather's good health with the family doctor, he immediately immersed himself in work.
Changhai Group was so big, and he had just taken over. He was ambitious and had made great plans to lead Changhai Group towards new horizons. Work naturally consumed him.
Certain things, those beyond the realm of reality, are difficult to believe without first hand experience. Hai Yuchen had never believed in such mystical things, though he admitted this scammer was quite creative.