Just realized yet another thing that makes no sense in this movie

Sure the headache inducing time travel angle causes a lot of problems, but something else occurred to me when watching this recently. Isn't it stated that the Godzillasaurus that was mutated by radiation during the war in 1944 became the Godzilla that destroyed Tokyo in 1954? The one that was killed by the oxygen destroyer?

So then how would removing it from the timeline before it was mutated prevent this current Godzilla (which is a different creature that was first introduced in 1984) from existing? Unless they're saying that the Godzilla from this series in the same monster from the original 1954 film.

I know that the Heisei Godzilla ended up being created anyway due to a submarine crash but the question still remains about the two different Godzillas in this continuity. He can wiping one from existence prevent the other? Can someone please elaborate on this?

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