Most of the R&D in China is done with private money. The government does contribute, but it's more long term guarantees than it is cash.
In a democracy, policy can change ever 4-5 years. Look at the US, it's been alternating between pushing renewables to banning them to pushing them to banning them again, over the last 4 administrations. If you were a company developing renewable technology, would you have faith that your investment in R&D wouldn't be banned by the time it reaches market? Doesn't even have to be a ban, just an administration that is hostile to your business, and an electorate that would rather roll coal than see a wind turbine 20km off-shore.
The Chinese government said that EVs were the future and it would ensure that future came quickly and stuck around. It made sure the infrastructure was installed, and promoted them to consumers as a way to reduce pollution. Loans for development were made available. And it stuck to that for the long term, not just the next 4-5 years.
Democracy can do that too, but not in a two party system. Look at European democracies where coalition governments are the norm, where the system is designed to prevent any one party gaining complete power. Planning is longer term, and there is more certainty in future policy direction.