9 years to build something that only last 20 seems a bit weird though.
The shrine is the previous generation teaching the next to build the shrine.
So if the shrine were to fall, then the shrine would eventually fall.
That is why the shrine must keep falling, so that it can keep being rebuilt, and so the shrine keeps standing.
Something is “weird” when it is absurd, which is to say something that is aimless or has an aim that is not in the service of an objective good. There’s a deviance from the nature of the thing, like intentionally growing a tumor on your forehead or having a tumor growing out of your forward and then happily refusing to have it removed.
Otherwise, what is said of things that are merely unconventional.
So in this case, is there not a purpose? Is the purpose not spiritual and instructive in some sense? Are you not imposing an inappropriate tacit goal onto this practice?
Or perhaps you find it weird because it is nowhere to be found within your conventions?
probably.
By contrast, Hōryū Gakumonji (法隆学問寺) is a 1350+ years old wooden structure more closely related to the themes of imported Buddhism long before the shinbutsu bunri (神仏分離) but in Japanese style. There are/were very large buddha figures carved into rock throughout Iran, Afghanistan, China during the Mongol period and also semi-contemporaneously c. ~7th century Japan's Usuki Stone Buddhas (臼杵磨崖仏).
https://en.wikipedia.org/wiki/Ise_Shrine#Rebuilding_the_Shri...
https://en.wikipedia.org/wiki/Seng%C5%AB
https://en.wikipedia.org/wiki/H%C5%8Dry%C5%AB-ji
Our stonemanship has unfortunately disappeared from lack of state support in the times the subcontinent was under foreign rule.
Finish one part of the building and the next part needs doing. And on and on it goes.