Why did China's traditional culture decline and when did it begin to decline?

The decline of China traditional culture began at the beginning of last century, and was abandoned in the middle of last century, which accelerated the decline. Today, after being abandoned for 60 years, it basically leaves only a few beards. Although it is inevitable for any nation to abandon traditional culture, a healthy nation should evolve its own culture on the basis of traditional culture, and through continuous evolution, an evolved traditional culture can cover and replace the original traditional culture. Only unhealthy ethnic groups destroy traditional culture by radical means and forcibly replace traditional culture with cultural forms without humanistic and historical basis. This is the case in China. Over the past 60 years, traditional culture has changed beyond recognition, but no cultural style can cover and replace it. The above, I don't know the reasons in detail, everyone understands.