The timelines were reorganized into a single timeline to prevent the Variants of Kang to dominate the Multiverse. To avoid the return of the Kang Variants, He Who Remains created the Time Variance Authority, an organization that prunes growing branches and Variants.
The so called Sacred Timeline was He Who Remains's solution to avert the apocalyptic Multiversal War of the Kangs waged by His Variants by altering the history of their respective universe's timeline/reality so they would instead come to be Him.
Years ago, he met multiple variants of himself who ended up launching a war that crossed time and space. To prevent this from sinking into chaos, He Who Remains created the Sacred Timeline and formed the TVA to prune any rogue branches.
What is the difference between the multiverse and the sacred timeline?
The Sacred Timeline from Loki is just one multiverse with infinite branches. Each branch is the time stream of one universe. Basically all the energy that exists in that universe from beginning to end. All those universes/timelines were bundled together in a halo formation.
LOKI Writer CONFIRMS How Variants Exist in Sacred Timeline EXCLUSIVE | MARVEL Explained
Did Dr Strange know about the sacred timeline?
SUMMARY. In 'Avengers: Infinity War', Doctor Strange looked into the future using the Time Stone and saw 14,000,605 possible outcomes of the war with Thanos. An MCU fan theory suggests Strange became aware of the TVA from 'Loki' when he established only one outcome was successful.
The Sacred Timeline is also prominently used to refer to a singular timeline, the main baseline, also known as Earth-616, which is the starting-point for all the timelines that the Time Variance Authority monitored.
The Council of Kangs, having deemed Kang too dangerous, chose to banish him into the Quantum Realm in an attempt to prevent a new war, since Kang was still seeking to conquer the Multiverse.
The Bombing of the Sacred Timeline was an attack planned and executed by Sylvie Laufeydottir in order to distract the Time Variance Authority so she could infiltrate their headquarters in an attempt to find the Time-Keepers and kill them.
He Who Remains, the first Kang variant in the MCU, was not a villain but actually had noble intentions in maintaining the "Sacred Timeline" to prevent timeline chaos.
The Sacred Timeline isn't just one timeline/universe, but it comprises of an infinity number of unique universes. “But then, the all-knowing Time-Keepers emerged, bringing peace by reorganizing the multiverse into a single timeline, the Sacred Timeline.
Lasting six years and one day, the Second World War started on 1 September 1939 with Hitler's invasion of Poland and ended with the Japanese surrender on 2 September 1945.
He said he took control of Alioth, the beast that consumes everything that was pruned from branch timelines and used it to win the war. The once and future Victor Timely said he created the TVA to maintain the Sacred Timeline and prevent other Kang variants from arising.
For the entirety of the MCU, through Loki Season 1, there was no multiverse. However, to the characters outside of the TVA, this "new" multiverse has also always existed.
Since Loki destroyed the Temporal Loom, the timelines were dying. The Temporal Loom was designed by He Who Remains in a way that it could only power the Sacred Timeline. When Sylvie killed He Who Remains, there was no-one left to regulate the Sacred Timeline.
Everything we know about the Sacred Timeline comes from He Who Remains and Miss Minutes. Should we really be so quick to trust their word? They point to the Sacred Timeline as the original chronology that must be protected at all costs, but we have to remember that both of these characters are liars.
Why were the timeline branches dying in Loki/MCU? Timelines need power to keep them alive and Temporal Loom acted as a generator to power them. Since Loki destroyed the Temporal Loom, the timelines were dying. The Temporal Loom was designed by He Who Remains in a way that it could only power the Sacred Timeline.
Loki, as it turns out, was the only one who could save the TVA—and so from the moment Sylvie killed He Who Remains, he was destined to need to hold the timelines in place. He's now Loki Who Remains, possibly for the rest of time.
Prior to his appearance in Quantumania, though, Majors made his MCU debut in the Season 1 finale of Loki, playing one (of many) variants of his villain Kang the Conqueror named He Who Remains.
He also ensures that some of the technology Kang will need gets invented (Tony's time travel machine). As he gamed this particular fight over and over, maybe more than 15 million times, He Who Remains chose this specific set of events. He caused Heimdall, Loki, Gamora, Black Widow, and Iron Man to die.
Like others from his native era, Kang ages at a slightly slower rate than modern humanity and is more resistant to the effects of radiation; though, he can be harmed by concentrated doses. He is an expert in time travel and the manipulation of time, and has mastered his future's advanced technology.
Earth-616, also known as the Sacred Timeline, is the main reality depicted in the MCU. Despite having been designated as Earth-199999 by Marvel Comics in 2008, Multiverse of Madness establishes the MCU as Earth-616, sharing the name with the primary setting of the comics.
Multiverse: Marvel universe is Infinite (probably) and there are infinite versions of everything. Sacred Timeline: Sacred timeline is a single branched universe that will eventually produce only one version of 31 century scientist Nathaniel Richards, that we viewers know by the name "He Who Remains".
She is an alternate version of Loki who helps him fight to overthrow the Time Variance Authority (TVA). She hopes to destroy the TVA and He Who Remains for stealing away her life, viewing herself as an agent of the universe itself. She is later forced to ally with a variant of Loki from 2012.
