What gave you the impression that it's "without too much sweat"? They sweated insanely for the past 6 years.

They also weren't starting from scratch, they already had a domestic semiconductor ecosystem, but it was fragmented and not motivated. The US sanctions united them and gave them motivation.

Also "good" is a matter of perspective. For logic and AI chips they are not Nvidia level, yet. But they've achieved far more than what western commentators gave them credit for 4-5 years ago. And they're just getting started. Even after 6 years, what you're seeing is just the initial results of all that investment. From their perspective, not having Nvidia chips and ASML equipment and TSMC manufacturing is still painful. They're just not paralyzed, and use all that pain to keep developing.

With power chips they're competitive, maybe even ahead. They're very strong at GaN chip design and manufacturing.

Western observers keep getting surprised by China's results because they buy into stereotypes and simple stories too much ("China can't innovate and can only steal", "authoritarianism kills innovation","China is collapsing anyway", "everything is fake, they rely on smuggled chips lol" are just few popular tropes) instead of watching what China is actually doing. Anybody even casually paying attention to news and rumors from China instead of self-congratulating western reports about China could have seen this day coming. This attitude and the phenomenon of keep getting surprised is not limited to semiconductors.