One thing I always feel very important about the whole Maeglin selling out Gondolin for life & freedom matter is…
Morgoth promised him lordship and Idril AFTER Maeglin already told him about Gondolin’s location and defense secrets.
Yeah obviously the promise of power and Idril might be what kept him in line and continue to cooperate with Morgoth after returning to Gondolin (can be interpreted in various ways from “the world is ending better take care of my own desire” to “the world is ending better preserve what I can still save”)
But the lordship and Idril were NOT what directly caused the initial betrayal.
Here comes my dumb headcanon:
Maeglin initially cracked not because of anything related to Idril and Tuor.
He cracked because of the torture & what Turgon did to Hurin.
When Hurin came to seek help nearly three decades after his imprisonment, Turgon assumed Hurin was released because he sold out the location of Gondolin for freedom. Turgon was overwhelmed by this assumption and let emotions run over his own judgement (again). He directly told the eagle “my heart is shut,” and refused to take Hurin in.
Of course Turgon changed his mind after calming down. But it took too long; the night fell and the eagles could not find Hurin again. From Hurin’s pov he was abandoned by his friend (or even a father figure), and thus was driven to complete despair, crying out in pain, accidentally letting Morgoth know the general location of Gondolin.
I think it is rather possible that Maeglin knew of this, at the moment or later.
Then when he got captured by Morgoth and put through tortures, he would realize he was essentially in the role of Hurin.
Turgon did love Maeglin. But Maeglin knew Turgon treasured Hurin too. The king treasured Hurin enough to make an exception and let the brothers leave the city to return home. Probably after Unnumbered Tears Turgon also built statues in Gondolin honoring Hurin. But when Hurin actually showed up at door and seeked help? Turgon immediately grew suspicious and assumed that Hurin betrayed the city.
And Morgoth could even tell Maeglin what really happened to Hurin. How Hurin endured torture for 28 years without betraying Gondolin, but was viewed as traitor and abandoned by the king of Gondolin anyway. How Turgon became the last straw that break Hurin into leaking the location. How ultimately it was thanks to Turgon’s closed heart that Maeglin got captured.
In a word, I think what caused Maeglin’s betrayal was him realizing that
Morgoth could torture him forever
No one from Gondolin would come to save him (And other realms had fallen so there was really no hope)
Even he suffered forever to keep the secrets, it was expected and not appreciated by Gondolin
Even if he found a way to escape back to Gondolin, he might still be rejected/executed by Turgon because no one was allowed to lead danger to Gondolin (according to “of Tuor and his coming to Gondolin”)
Morgoth already knew the general location, no matter he cope or not Gondolin would eventually be found. And then Turgon would believe it was him that betrayed Gondolin anyway.
So yeah.
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I just think Turgon rejecting Hurin should has more long term damages than letting Morgoth knew the general location of Gondolin (which was already very bad).
It was something that could send out all the wrong messages and greatly damage the morale. I always imagine the event was kept as a secret, and even most of the lords did not know about the matter.
I think Tuor absolutely was kept out of it and he never knew he was so close to meeting his uncle until after the Fall.
Idril probably knew it, and helped to keep the secret from Tuor, and felt guilty. And that was one of the crucial moments that made she further distrust Turgon’s judgement. (I want all the “my father did an evil thing and I am helping him to keep it as a secret” angst)
Maeglin… Actually fought the losing war along with Hurin and Huor and was there when they sacrificed themselves to help troop of Gondolin escape. IDK I think that’s another “silently pondering in horror” moment for him. And he kept thinking about it, and kept trying to not thinking about it, until Morgoth forced him to think.
