Things are becoming clearer
1. Didi was repeatedly warned by Chinese regulators not to list in US. It still went ahead.
2. Under US regulatory law, data of Didi (Chinese citizens) wouldve be available to US investors (aka CIA)
3. Didi and for that matter companies like Alibaba, Tencent, JD host extremely critical data about Chinese citizens and are told to IPO in HK instead .
4. Another rumour suggests that Didi went ahead as Chinas new draft law over data would've made data collection more stringent and launching an IPO after this would've affected their IPO price.
All in all Didi wanted to earn money and expand globally while compromising on data of Chinese users. While the company will say that it stores all data in China, that's not the point. Question is about access which US would've gotten one way or the other.
Companies aren't punished for fun there's always a reason behind it. To think that Xi holds a grudge against a frigging Ride hailing app is laughable. (Some users made that assertion here)