There are trillions of dollars in capital floating around looking for a better place to park it than treasuries. Major infrastructural projects like semi fabs should be a no brainer - the risk is not that high due to evergrowing demand and the trust that governments won't let an Intel or TSMC fail.
Even just look at the VC landscape - there was $621 billion spent in venture capital globally last year, which is one of the worst ways to invest your cash.
Point being there's plenty of capital out there for giant projects like building fabs, I just don't think it's sexy enough yet or the financiers haven't taken a deep enough look while governments are expected to make the first moves.