Similarly, when the entire world has used the single-world hypothesis almost exclusively until the recent past, it isn't unfairly privileging it to still consider it a major contender.

It's not a major contender because of hearsay of powerful evidence like we have with legends. It's a major because it's been unfairly privileged ever since someone thought of it. It's far more complicated than the hypotheses that they haven't thought of, so by Occam's razor, it's far more likely to be a hypothesis that nobody's thought of than that one.

It's not like a legend about the city of Nazareth. It's not even like a legend about the birth of a god. It's like concluding that there's a god because life has clearly been optimized, and you haven't thought of any alternative hypotheses yet. Once Many-Worlds has been suggested, it's like concluding there's a good chance of there being a god, because you would have thought there was one before you thought of the alternative hypothesis.

Just because you haven't thought of an alternative hypothesis doesn't mean there isn't one. It does mean that you have to discount it on the, rather high, chance that it has already been disproven. Most have. But if there's enough alternatives, if your hypothesis is complicated enough from the beginning, there's bound to be an alternative hypothesis that actually explains it.