Warning-your mind may be blown.
The time travel goofs in Godzilla vs. King Ghidorah are in a disturbing abundance. They violate so many laws of time it altered the series completely. First: The Grandfather Paradox. The futurians go back in time to get rid of Godzilla. They move the godzillasaurus to the present removing him from history. This means that there was no Godzilla to get rid of which means the futurians could never get rid of him which means Godzilla exists for them to get rid of and it just goes on and on. They return to the future to find that King Ghidorah replaced Godzilla, but everybody remembers Godzilla when he never existed. This is also shown with Destoroyah, Biollante, and SpaceGodzilla. They have records of the battle between Godzilla and Biollante, even though it never happened and Biollante never existed. They have the ability to say SpaceGodzilla was created by Biollante. Destoroyah could not exist because the original Godzilla was never around to die by the Oxygen Destroyer. Second: you cannot exist with yourself at any moment in time. MKG comes back go defeat Godzilla, while his comatose body is lying on the ocean floor. One of them would have to disappear, which would make MKG disappear either way. This brings me to think that the entire Heisei era after GvB takes place in a paradox where time cannot be altered by an outside force. This leads to a connection with final wars where, shortly after GvB, he was tracked down and frozen in the Antarctic. Third: This Godzilla is the original Godzilla. The nuclear sub mutated the Godzillasaurus into Godzilla, making it the first Godzilla. It is the same Godzilla as the 1954 one.