@The Loki Lady To address your confusion with the time travel:
The way I see it now is that the time-keepers didn't actually destroy the entire multiverse and create one Sacred Timeline, but instead picked a Sacred Timeline and began to alter all new universes to match that of the Sacred Timeline. This is why they can travel to a universe currently in 2050 while the MCU as we know it is still in 2024. All of these universes are still in accordance with the Sacred Timeline even though slight difference occur, such as one of them having Loki and Mobius in Pompeii, or Captain America fighting himself in 2012 although this wouldn't have happened in the MCU, as they would have at least remembered this incident as it was happening. Therefore I believe that the TVA is just making sure that all universes stay (mostly) in accordance with the Sacred Timeline, and Nexus events are just what happens when something starts happening in a universe that alter it away from the Sacred Timeline. You can almost think of it more as traveling throughout the multiverse to universes that were created earlier or later then others.
I think this works really well right now because this is how time travel worked in Endgame, and Mobius explains that they don't know what happens at the end of time, but when that does happen their job will be done. I think he means that the end of time will be when every universe in the multiverse ultimately reaches the end of the Sacred Timeline, because then the TVA's job will be accomplished and the Sacred Timeline will be established and unalterable throughout the multiverse.
Of course new info might discredit this, as Lady Loki might suggest that their is a multiverse that the TVA doesn't know about or the Time-Keepers might be hiding something from us.