Loki Disney Plus

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Scorpius the Allfather said
I think it's as simple as what Mobius said, Loki falling for a variant version of himself created the nexus event. And Loki was about to tell Sylvie how he felt about her and right before he got the words out, he said he's never felt that way before so that tells me that he's not supposed to fall in love with ANYONE so falling for his variant might be the actual cause and whoever he fell for doesn't really matter.

Brock Meaux said
Loki and Sylvie "fell in love." Whether that means romantic love, or some kind of meta self-actualization and acceptance, or just two Lokis actually caring about someone else, it was enough to trigger the alarms. Which, them doing that would be more significant than Sylvie hiding, living a day-to-day life at Roxxcart waiting for the apocalypse. And Mobius did say that the sensitivity of their monitoring was turned all the way up at that point, as they were looking for them.

I don't think the sensitivity of the monitoring is relevant, because while Mobius did say it was magnified so it would set off alarms "if somebody steps on the wrong leaf," when it actually happened, he said it wasn't someone stepping on the wrong leaf and that they'd never seen a branch like that.

But the main problem with that theory is that it doesn't actually get around the apocalypse problem. If Loki 'fell in love', it shouldn't matter. The timeline would remain exactly the same. A Loki in love crushed by an entire planet has exactly the same impact on the continuing timeline of that reality as a Loki not in love crushed by an entire planet does, that is, none at all. That's what allows the whole 'hiding out in apocalypses' thing in the first place.

So that in itself doesn't really cut it IMO. The only way that should be able to create a timeline branch is if what happened meant Loki wouldn't die where previously he would, which would then have meant he had a continuing effect on that timeline, thus allowing the creation of a branch.

tomwaits said
Maybe the Nexus event started happening because Loki and/or Sylvie are not supposed to die and their death would cause a massively destructive event for the multiverse.

But that's an interesting thought! From the point of view of that reality, I don't think it would be that, because the Loki and Sylvie on Lamentis aren't that reality's Loki, he's already dead, so their dying there should be irrelevant. But if the TVA's 'sacred timeline' encompasses multiple timelines (which it appears to, to at least some extent, with (e.g.) Steve Rogers living an alternate life out), then perhaps?

It could also just be that the sacred timeline, nexus event, things are much more arbitrary than we've been led to believe.

Or it could be that I'm overthinking this. Definitely that one.