The giant Buddha is very high, 7 1 meter, which is as high as a mountain at close range, so "Buddha is a mountain";
Simply put, it is the unity of Buddhism, which embodies the idea of the unity of man and nature and belongs to Taoism and Buddhism.
If you simply say that just because you are very old, it is not Li Bai. Can spread to the present, because it has a deeper meaning, Buddha and mountain, under certain conditions, can be transformed, just like Yin and Yang.
Because Buddhism prevailed in the Tang Dynasty, Wu Zetian respected Buddhism, but the emperor surnamed Li claimed to be a descendant of Laozi (Li Er), so Taoism also prevailed, which contributed to the unification of Buddhism and Taoism.
So Li Bai had such a poem at that time.