In the Heisei continuity we know that the Godzilla that appeared in the 1980s through the 1990s as well as its adoptive son are mutated members of the "Godzillasaurus" species.
Now the individual from 1954 was not explicitly stated to also be a mutated dinosaur like its successors and going off the Showa continuity it was already gigantic and the radiation just scarred it and gave it some abilities.
However for the sake of simplicity we'll say the 1954 individual was also a mutated Godzillasaurus, just not the specific individual living on Lagos island. After all if there are living survivors and eggs there has to be a breeding population at least into recent history. Given how few Godzilla there are however we can probably conclude their numbers are drastically small and they might be effectively extinct due to being in the single digits. Very large animals tend to live an extremely long time so it is also possible that the dinosaur on Lagos Island might have been decades or even a century or more years old and their breeding intervals are very slow.
Essentially my hypothesis boils down to, the Odo Island mythology was created through thousands of years of very infrequent contact with Godzillasaurus individuals.
Archosaurs, the family of reptiles that contains pterosaurs, dinosaurs, crocodilians, extended relation, and due to also being dinosaurs themselves, birds; all exhibit signs of parental care. The offspring are cared for by one or both parents until they are old enough to go off on their own. Once the young are old enough to go off on their own, they might roam very wide expanses of ocean to find the territory unclaimed by an adult. Odo Island might be pretty far from Lagos Island, but it is not uncommon at all for animals in the ocean to wind up hundreds of kilometers away from their normal range on sporadic occasion. And the Godzillasaurus species is at least heavily implied to be amphibious given that the baby had no trouble swimming out to sea and they are seen living on islands. One could even suppose the reason they survived the mass extinction event was because unlike other large theropods, they were able to exploit both terrestrial and marine resources.
So, we'll say several thousand years ago, a young Godzillasaurus adolescent, already gargantuan size given that they're fully grown stature is as tall as a Tyrannosaurus is long, happens to come upon an unclaimed island. This island is Odo Island and given it is an amphibious carnivore it goes to town on the local fish and cetacean populations. The island however is occupied by a group of humans. Now these humans are no threat to the Godzillasaurus, in fact it doesn't even really noticed them (as remember the individual on Lagos island only turned aggressive due to the chaos of the war). Given that fish and cetaceans often forage closer to the surface at night, the dinosaur might also mostly come out at night. This furthers its terrifying appearance as any of the islanders that might glimpse it would only see it out at sea or at night when it's body might be obscured. And if anyone did get a good look at it, they would be utterly terrified. if it came at a certain time of year it might also be arriving at the same time heavy monsoons and storms ensue, further adding to its mystical image because it might be associated with hurricanes.
The islanders notice of fish and cetacean population dropping, lowering their food resources. By now word has spread about the sea monster or dragon they've sighted and this unnerves them more. They have never seen a creature like this and they would likely not even think it was a flesh and blood normal animal, but some sort of force of nature or supernatural entity. There might've been attempts to fight it off but with their primitive technology they stood no chance. Odo Island might not be in an area that is able to quickly refresh its stocks of fish and wildlife, possibly due to habitat or currents similar to Bermuda. So both the Islanders and the dinosaur become increasingly hungry.
The Islanders, knowing they can no longer fight it, attempt appeasement. After all if this is a supernatural monster sent to punish them or seize their livelihood, maybe they can appease it to make it go away. So they offer up first the fish they have. The dinosaur, who had already been eating fish, eagerly accepts it. Except it won't leave. In reality it won't leave because it was just fed and might start associating humans with food like many wild animals, but to the Islanders it might come off as they didn't offer up a good enough sacrifice to appease this supernatural beast of the sea.
If they attempted to give it offerings of finery and valuables, the dinosaur would completely ignore them as such concepts are completely lost on it. And it's getting hungrier while increasingly associating humans with its last good meal. Out of desperation the Islanders, who had been feeding it fish sent out on rafts, offer up one of their own. The dinosaur, hungry and having that food association, attacks the raft and consumes the human aboard. Primates in general are not very palatable to most predators and this might come in to play. Between the human flesh it just consumed and maybe the finery the poor virgin was dressed up in, the Godzillasaurus finds its meal disgusting.
This region does not have a sustainable food source, the humans are now annoying, and it just had something that tasted revolting. It's leaving to find a new territories somewhere else. To the Islanders however it looks like the monster has finally been appeased and the very sacrifice, that unbeknownst to them tasted horrible to it, was the very thing that finally made it leave. A new tradition on how to deal with the sea dragon "Gojira" is formed, feed it fish and virgins tied to rafts with the best stuff they got.
Decades later another young Godzillasaurus adolescent comes to Odo Island looking for a territory. The Islanders don't realize, because they don't think of it as a flesh and blood creature, that this "Gojira" is not the same individual as last time. To them it's the same immortal sea dragon returned and a new sacrifice will be in order. Over the centuries, in increasingly slower intervals because the species is gradually going extinct, the cycle keeps repeating. Perhaps the last time was in the 1870s, long enough that memory has faded quite a lot and the creature(s) became increasingly mythologized. The only ones who remember the last incident by 1954 were either extremely young at the time or only got the information secondhand from their parents or grandparents. But as soon as signs show that a giant creature has returned, the Islanders realize the legend was true.
However with more modern technology as well as gestating of memory to where no one can recall the last time anyone tried to kill "Gojira", they attempt to mount an offense. This is why they're running up that hill following the tracks carrying weapons. They could never have imagined the monster that terrified their ancestors has a descendant that due to nuclear radiation would become the King of Monsters.
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