Because Li Ka-shing was worried about the future safety of his son and family, and was worried that Zhang Ziqiang and his group would retaliate against the Li family in the future, plus 1 billion was not a problem at all for Li Ka-shing, so Li Ka-shing did not send anyone to retaliate. Zhang Ziqiang, instead chose to cooperate with Zhang Ziqiang.

The first reason is for safety reasons

We all know that Li Ka-shing’s son was kidnapped by Zhang Ziqiang. Li Ka-shing did not send anyone to retaliate against him. That is because Li Ka-shing knew very well that if It is very simple to find someone to kill Zhang Ziqiang yourself, but Zhang Ziqiang is not alone, they are a gang. If Zhang Ziqiang's gang cannot be wiped out, it is better to spend money to prevent the disaster and keep his son and family safe.

The reason why Zhang Ziqiang dared to kidnap Li Ka-shing's son was because he was not a person, but a gang, with 5 key personnel and 26 other auxiliary personnel. These people are brave and ruthless desperadoes who can do anything. In 1996, Zhang Ziqiang failed to kidnap the Macau gambling king and even threw Molotov cocktails at the gambling king's home. Later, Zhang Ziqiang even went to the mainland to buy 800 kilograms of explosives in order to rescue his accomplices from prison.

The second reason is that 1 billion is not a problem for Li Ka-shing

Li Ka-shing chose to cooperate with Zhang Ziqiang because Li Ka-shing clearly understood that 1 billion was just a drop in the bucket for his wealth. In addition, Li Ka-shing clearly understood that it would not take long for him to earn back 1 billion, but if his son was gone, he would be gone. Therefore, Li Ka-shing would rather give money than see Zhang Ziqiang hurt his son.

To summarize, Li Ka-shing clearly understands that there is no need to fight desperadoes for 1 billion yuan. They just want money. If they resist and provoke Zhang Ziqiang, they will kill people in minutes.