Didi committed the sin of going ahead with a US listing against explicit orders from the government, in the context of an economic cold war with the US. China has plenty of capital, it's not as if we're in the 1970s and the US is the only way to go. You can bet that if JP Morgan Chase wanted to shift its headquarters to Hong Kong, the US would also take swift action. What the Chinese are doing with foreign listings is not all that different from what the US does with CFIUS.
Wanting to preserve privacy from private companies is not at all inconsistent with wanting the government to have total surveillance power. There are many domains where government has a monopoly, from issuing currency to the exercise of violence.
You will note Xi is cracking down in other areas that are not a plausible threat to the CCP, like bitcoin miners or the educational tutoring arms race. Sometimes, the stated agenda is the actual agenda.
1) Where a company derives it's revenues, is not necessarily where it creates value.
2) Search is not a side-show, neither is mapping, Chrome, v8, Android, Google Cloud, Go, Flutter etc. - and frankly neither is advertising.
3) Advertising is valuable. Only really those who've never worked in business don't realize this. Companies don't spend gazillions on it for no reason. Lack of efficiencies in marketing are obvious, but so are they in other fields.
... also:
"China has plenty of capital, it's not as if we're in the 1970s and the US is the only way to go."
This little sense as China has it's own central bank, which is politicized, and Xi makes his own capital out of thin air.
China never needed 'US Dollars' for anything. They needed 'US Buyers' and to steal 'US knoow how and tech' - but they never really needed foreign direct investment.
"Xi is cracking down in other areas that are not a plausible threat to the CCP, like bitcoin miners"
No, BTC is one of the biggest threats to the control of the CCP (and other financial institutions) because it puts economic activity completely out of his control - especially trans national control.
'Crypto Currencies' - or any for of economic freedom outside the purview of the CCP - is probably the #1 threat to the CCP - more than military, or social upheaval. BTC is obviously too small right now to be a problem, but it balloon quickly putting everything outside his power, and the rest would follow.
I don't even get it why you bothered to mention Ant, I wouldn't feel sorry for comsumer loan companies in another lifetime. You claim it to have pushed economic growth, that's the same as saying the pre-2008 housing market in the US is a huge pillar of economic growth, and look at where that lead us.
Not only is the premise that 'DiDi' etc. do not create 'real value' simply false, the notion this is Xi's primary concern is isn't true either.
Xi's #1 concern is power and control. It's ridiculous that they're talking about 'protecting people's rights and warding off monopoly' when they're literally doing the opposite in Orwellian terms.
There's no 'hollowing' of the economy due to any of giant's usage of data. While competition is a concern, it would be really bad industrial policy to consider 'chips' somehow more important than the things you can do with them.
Ant is consumer credit where there was none before, and that's a huge, huge pillar of economic growth especially on the domestic consumption side where Xi wants to push the economy.
The notion that Google et. al. are 'middlemen' is beyond wrong.
Xi has also stopped these companies from listing in the US, which isn't good for anyone but the CCP.
This is mostly a game of power, not industrial policy.