Nan Feng was furious that he was being falsely accused of being involved with a mafia gang, even if those criminals might have saved his daughter. Therefore, he sent people to investigate Tong Huan. Even though Tong Huan had done her best to clean up her family's act, generations of history couldn't be wiped off just like that.
What Nan Feng did, turned the two siblings against each other.
Not long after that, Tong Hui's forces were suddenly pressed in from many other gangs at the same time. Tong Hui was heavily injured and presumed dead. The Tong Family's underworld influence was heavily impacted. One year after that, Tong Zhan was assassinated and the Tong Family lost another leg to stand on. At the same time, Nan Zheng and Tong Huan supposedly died in a 'car accident'.
A mess was dropped in the lap of the youngest Tong siblings, Tong Le. Even though Tong Le hadn't graduated from university then, he had no choice but to take over lest the family collapsed.