It was because Jiang Wanling had taken medicine and had been on psychiatric drugs for some time before the incident that everyone assumed she had committed suicide and no one suspected Cheng Yuansen.
The only one who should have investigated the matter, Old Master Jiang, fell ill and was hospitalized due to continuous blows, so he didn't continue the investigation.
Jiang Wanling was rescued, but due to her severe injuries, she was in a coma for a long time. With Song Huaizhi's entire focus on her wellbeing, he didn't think to investigate the matter either.
Later on, all traces were cleanly erased, so even if someone had suspicions, there was nothing to be found.
If it weren't for Jiang Wanling's recovered memories, no one would have ever suspected that Cheng Yuansen was behind Jiang Wanling's attempted "suicide".
