I have some thoughts, sometimes, about a universe where Pengolodh the unreliable narrator strikes again.
Fingolfin's host sees the ships burning and has thirty years of pain and awfulness to stew in disgust and fury. If they get to Beleriand and someone from Feanor's host tries to tell them something like "oh we didn't burn the ships, [other reason for big naval fire] happened!" then Fingolfin's host is never going to ever accept that.
They'd think it's the notoriously morally corrupt Feanorians telling lies & trying to manipulate people again, to cover their own asses or not take responsibility for their actions or try to stop the Icy Bois from being mad at them. It's clearly not true.
Then we have everything that happens in the first age, and all the accounts get confused and mixed anyway, and by the end almost all the feanorian followers are dead and no one is going to start being a feanorian apologist bc they will literally immediately get murdered. Like many other things in the first age, only one version of events survives, and it's not necessarily the true one.
"Feanor totally deliberately did an evil thing and set all the shops on fire and his son with them and he laughed while he did it" does smell a bit of anti-Feanorian propaganda, even though it does also completely make sense in canon given the direction Feanor went in. But its eaually plausible to argue that ideas of Feanor as an irredeemable villain totally blew up after the first age, and this was one of them! It would also explain the competing narratives about Amrod's fate if it was another rumour that sprung up out out of anti-Feanorian sentiment.
So what actually happened? Two takes.
1: something else caused the ships to catch fire. It's also entirely plausible that they weren't in good enough condition to sail back after the absolute bashing Uinen, Ossë & Ulmo put them through in the aftermath of the First Kinslaying. I don't like this one as much, because it makes the Feanorians completely blameless in the ship burning, which I think is boring and unrealistic and somewhat of a cop out. But it's fun to play with lots of alternate ideas of canon.
2: I like the idea of the timeline being a bit wrong; it's all dark, there's no days, the host of Fingolfin has no way of knowing how long it took the Feanorians to sail to Beleriand or how long they were there before the fire became visible. And I think the rest happened in quick succession;
they land, fight alongside Cirdan's people as in canon
Maedhros: can we send the boats back now? What about Fingon? Uh, I mean, our host and supplies and army I'm thinking totally strategically here
but Feanor is high on the victory of battle and there's fire in his blood, he wants to press onwards, he doesn't want to be stuck with the boring stuff of ship supplies and sending them back for his awful half brother.
and what if he can defeat morgoth without fingolfin
so fairly soon afterwards, the battle against Morgoth's larger forces is fought.
Feanor dies. "even in the hour of his death," Maitimo goes to parlay and is captured, his whole host slain.
The effect that this has had on the entire Feanorian host is- awful.
They've stepped from a deathless paradise where they thought they knew grief and darkness but they didn't, to a land where your might and your story arc don't matter, because anyone can die.
Even in the hour of death, Feanor knew the Noldor assault was hopeless. Maedhros goes to the parlay because maybe they can't get through by military might but if there's any chance they can win this and fulfill the oath that they're just now realizing they swore without knowing the truth of the world, or of doom- but he fails too.
This world is terrible beyond Maglor's darkest dreams. He sees that there's no hope, he's consumed by despair, and if he can save anyone at all...
He puts the ships to flame.
Go back, he means, go back while you can, go back and live.
They don't.
