The fountain of life doesn't know that he reincarnated. It only knows that some changes were made to Ragnarok's divine ability and that he awakened the original one. It doesn't know that Ragnarok made the changes but such a thing couldn't escape the notice of the fountain of life. But the fountain of life didn't do anything about it. The Fountain of Life chose to simply watch.
The fountain of life is a powerful entity. It is not threatened by Ragnarok despite sensing that he has a very powerful soul. Ragnarok surely has potential but potential doesn't equate to strength. Potential needs safety and time before it can become Strength. A dead genius is no different from a dead moron.
The most important reason why the fountain of life chose to abstain from killing Ragnarok for breaking the curse is that it is in a stalemate with the demon God of Carnage and it wants Ragnarok to help it. These are dire times after all.
The fountain of life doesn't expect Ragnarok to help out of the good of his heart. From the little it has seen about him, Ragnarok has very little good in his heart. But Ragnarok has to help out of necessity. He has to help or the demon God of Carnage will kill him.
The demon God of Carnage is not going to target him personally. The aim of the demon God of Carnage to subjugate all life and propagate Carnage endlessly will surely lead to it facing off against Ragnarok. So the Fountain of Life chose to watch instead of taking action to eliminate Ragnarok.
The fountain of life is so powerful that it has the entirety of the plane under its surveillance. So it noticed the creation of an Emperor immediately too. It would have noticed even if it were not that powerful. After all, the curse on the Warrogs has been deactivated twice on the same day. So it noticed this unborn future Emperor. The will of the plane also noticed the creation of the Emperor.
The will of the plane is the second entity that witnessed the creation of a future Emperor. But unlike the fountain of life who could afford to wait and see, the will of the plane is very desperate and anxious. The will of the plane is being threatened directly by the demon God of Carnage. It is facing an existential crisis because even it, a mere will, is not safe from the hands of a demon God.
A demon God is a vile universal virus. It will spread and rewrite everything it comes into contact with, be it spiritual, elemental, or physical, to create more of itself. The will of a plane is not safe from it either. The will of the plane is connected to every living thing within the plane so the demon God of Carnage can reach it through the living.
In fact, it has been fighting a losing battle with the demon God of Carnage for hundreds of years now. To a demon God, there's no better meal than the consciousness of all life within a plane. It is a delicacy to it just as much as the heart of a world or world god is to a Chaos entity.
The will of the plane was losing at the start of the battle and it is losing faster since the demon God is also simultaneously attacking the living things in the plane while directly attacking its will. The will of the plane can be likened to the ultimate Paragon. It is connected to every living being in the plane. It is unfortunate that it cannot use that strength personally. So it needs a worthy defender that it can bestow its strength to.
There hasn't been a worthy target for the position of defender of the plane these past few hundred years. The tree people dominate the plane but they are also the favorite target for the demon God of Carnage.
The tree people are vulnerable to the sin of Carnage. It will be game over if the will of the plane makes a connection with one of the tree people only for that tree person to be turned into the spawn of the demon God. That will create a direct connection to the will of the plane for the demon God. In summary, that will be the literal end of the plane.
The will of the plane didn't have a good choice apart from the tree people. The other races are weaker and don't have a divine ability. The Warrogs are good but they have been crippled by the fountain of life so they can't fully utilize the boost from the will of the plane. They still have their connections but the boost will go to waste because there's nothing to use it for.
The fountain of life diluted their divine ability with the fragments of the law of life on purpose. It ensured that the will of the plane will not be able to use the Warrogs to fight it. So the Will of the plane didn't have a good choice that will fully utilize the power of the plane. That changed when Ragnarok appeared.
The will of the plane would have chosen him immediately if his boost was aligned toward the living, not the dead. The Will of the plane represents the will of the living and the power gained from them. That power would have gone to waste on Ragnarok. But the will of the plane wasn't disappointed. Another opportunity arose because of Ragnarok and it took it.
It made sure that Ragnarok's existence successfully invoked the creation of a future Emperor despite the resistance of the curse of the fountain of life. This new unborn Emperor is the perfect vessel for its power so the will of the plane selected her.
The will of the plane selected the Empress as the child of the plane. It created a bond of power with the unborn fetus. It didn't wait for it to be born before it made the selection. It wasn't going to leave anything to chance. It also wanted to craft the empress into the perfect weapon to use against the demon god.