What made this historic retard in Buddhist Pagoda between Shilla Dynasty and Koryeo Dynasty.

20171030

There was a mistery in Buddhist Art History in stone sculptures.
The thing is that the stone sculpures of Shilla dynasty is more precise and better in every aspect than that of Koryeo Dynasty, even though Koryeo Dyansty seceeded in Shilla Dynasty.
It must be a common sense that the technique have been progressing as time flows.
But in Korea, this common sense did not fit in Buddhist stone art in two dynasties.
The skill of Shilla dynasty which was former than Koryeo was absolutely better than that of Koryeo dynasty.

I don't know how I could explain this phenomenon.

Let's look at the pagoda and compare each other.

At first Shilla dynasty style. Below was the pagoda of Soo Deok Sa.
Actually the pagoda of Soo Deok Sa was estimated as an early work of Koryeo dynasty which was strongly influenced from Shilla dynasty. The pagoda of Shilla dynasty is much more beautiful and well balanced than that of early works of Goryeo dyanasty.

Below was the Koryeo dyanasty style in Gwan Chock Sa temple

Do you have any idea about what made this historic retard in Buddhist pagoda ?