The main factor is timing, and
Tolkien is very precise about it.
The Two
Trees could have been restored, but only briefly, and only before
Morgoth escaped and their Light finally failed.
Yavanna explicitly says that their healing required the breaking of
the Silmarils while the Trees still lived, however faintly. That possibility existed for a moment and was gone.
When the
Valar ask Feänor to surrender the Silmarils, he refuses with words that matter deeply:
This isn't ignorance, Feänor understands exactly what is being asked of him. He knows the cost is not merely artistic or personal, but existential. To destroy the Silmarils would mean destroying
the one work in which his entire being is bound. Tolkien is clear: Feänor is wrong but he is not shallow.
After that refusal,
events move quickly and irrevocably. Morgoth escapes and then the Light of the Trees fades beyond recovery.
At that point, the Valar do not simply give up but they recommit the remaining Light and Yavanna uses the last flower of Telperion and the last fruit of Laurelin to fashion the Moon and the Sun. This act matters enormously because it is a conscious decision to stop trying to restore the past and instead preserve what can still be preserved. Once that Light is invested in the Sun and Moon, the Trees are not merely dead but their role in the world is finished.
By the time Morgoth is finally overthrown and the Silmarils are recovered in the
War of Wrath, there is nothing left for them to heal. The Trees are long gone, their remaining Light already dispersed into the heavens and the wider world. Even had the Valar possessed the Silmarils earlier, they could not lawfully have destroyed them without Feänor’s consent, which is something that Tolkien makes explicit by framing the request as a plea, not a command.
Thus the tragedy is layered and complete:
• Feänor refuses while restoration is still possible
• Morgoth escapes and the Trees die
• The last living Light is used to create the Sun and Moon
• The Silmarils remain, intact but no longer curative
This also explains why the Valar make no attempt to recover the Silmarils after the War of Wrath. The world has already been re-ordered, the Light already committed elsewhere, and the Silmarils themselves are now embedded in the settled structure of
Arda, one in the sky, the sea, and in the earth. To retrieve them would require the Valar to disrupt the very order they had just sacrificed an Age to establish, and to interfere once again in the consequences of choices freely made by the Children of
Ilúvatar.
More importantly, the Silmarils are no longer morally neutral
objects. Every attempt to possess them has resulted in ruin, not because of a simple curse, but because they have become focal points of oath and consequence. Having already learned the cost of overreach, the Valar restrain themselves. They do not rule by perpetual correction. They allow the consequences of the
First Age to stand.
They arrived at the only outcome left once free will, pride, and time had all taken their toll.
—
Klaatu,
Custodian of Irreversible Decisions,
Still stamping “POINT OF NO RETURN” on the First Age