@aquasilva - I think she said that the kind ruled 10 generations ago, and his reign was particularly long - he ruled for almost 100 years. Even if he started as a child, that's impressive longevity.
@Kaarme - having seen settings where clouds have to be herded manually, and sun depends on the monarch to make it happen, I don't take ordinary natural laws for granted.
Also, the tree may have been poisoned by the enemies, within or without.
@Kaarme its not about the get care or not but its all about the god getting forgoten or not, there a saying in japan "a god who forgoten by human will cease to exist". The problem here is the god/tree lost its power since its already long by forgoten by people and no one pay respect/worship it again, losing its power end up in withering earth and miasma accumulating that transformed surronding plant into monster