The government was both going to demand, and fund local companies creating a competing product and was already doing so long before sanctions arrived. Nothing about the sanctions sped up the process in the least. The Western sanctions had almost 0 bearing on accelerating local chip production, but it did do a GREAT job of limiting their ability to buy the hardware required for advanced fabrication.
You also seem to have a belief that a "monopoly" in China is anything remotely like the West. It's not a free market, if a company in China tries to gouge the market or take it in a direction that's not approved at the expense of what the party wants, their executive leadership will quickly find themselves on the outside looking in (if they're lucky) or sitting in a jail cell if they aren't. See: Jack Ma
Semiconductors were core to the "Made in China" strategy the party was pushing in 2014...
https://www.mckinsey.com/industries/semiconductors/our-insig...