The Leviathan https://villains.fandom.com/wiki/Scarlet_King is an entity formed as the manifestation of the tension between the modern world and the pre-modern world and the rage it creates. Originally it existing as the concept of there being something greater than man, such as gods or the supernatural, that could not be controlled or reasoned with. Modern ideas spurred on by the scientific revolution and the enlightenment encouraged humanity to understand their surrounding environment with a new perspective that focused on rationality and proven facts based on trial and error analysis. This concept of the Leviathan was then shaped by the encroachment of modernity into the old world and the clash between the two. An organization known as "The cult of the Leviathan" seeks to reincarnate their deity on the mortal plane directly in the form of a human child with Leviathan's soul. The group seek to return the world to its pre-modern age where humanity After being born into the world through mortal means, he will grow up to become the living manifestation of their god and subjugate humanity to his rule, with the cult at the helm of power. This plan would have severe consequences that are more far reaching than even the cult had planned.
Time works in a linear fashion, with the past, present, and future all occurring simultaneously. The laws that govern the universe (gravity, physics, etc.) work in tandem to create our reality and what counts for normalcy, acting as stabilizers to keep it together. However, reality is fragile, and can be disrupted by an outside force that violate those natural laws meant to keep it stable. Manufacturing a deity from scratch has caused ripples in the timeline, affecting its linear in all directions and changing it forever. These ripples have altered history, retroactively inserting the deity into specific moments and events, forcibly making it part of the timeline and effectively retconning history. Now that the new reality has overlaid with the old one, this has created a paradox: the cult has essentially created the very god that they worship, which has led to inconsistencies within the space-time continuity. The god-child was born at a specific point in time, yet has always and will always exist within the past, present, and future.
However, there have been significant amounts of individuals throughout time who have become aware of these contradictions, both in the past and future. They have noticed the retcon and retain memories of the original timeline which no longer exist, as history has been rewritten to accommodate this new god. The world does not remember this past, and regard these people as crazy or liars. For them, their lives has always been this way. This is similiar to a software upgrade, such as going from a windows 95 to a windows vista. For those others, it is like they went to bed and woke up in an alternate world with a revised history. Since they were part of the same change as everyone else was, how could this have happened?