It probably is a chicken-and-egg problem. Speaking from my own experience, the comparatively very low software engineer salaries in France drove me to freelance (mostly for foreign clients), and later emigration.

There is simply very low demand for high-skill software developers. Compare the job ads in Paris vs. NYC for instance: the Paris tech ecosystem is overwhelmingly hiring for dirt cheap roles on outdated technologies.

I think it's a mix of culture, and the lower upside French startups can aspire to due to market size and heavy tax/bureaucracy burden.