Sounds like a 19th century Congregational breakaway movement but it’s the principle that if things have matched up well in the past there’s no reason to believe they won’t continue to match up. In linguistics an example would be if language contact results in vocabulary borrowing but no extensive restructuring of grammar, then we can expect that to be the case in any language contact situation. Caution is advised, of course.
This contrasts to explanation of a deus ex machina type where one speech community would change language totally with no outside pressure, just b/ the new language has putative superior quality. I remember a book I used to check out of the municipal library periodically that tried to establish that some Native American languages were really Old Norse, Vikings having so overwhlemed the indigenous population that they dropped their own language and adopted that of the superior beings.
Well, the indigenous people of Mexico sort of dropped their languages – not entirely, by any means, but they do adopt Spanish when integrating into the large society – when they encountered Europeans, but on a scale quite different from what was positied for these magical Vikings.
But…. is it true a fossilized lutefisk was found at a Iroquois longhouse site?