EDIT: /u/Masaryk has pointed out that linguistic and cultural conservatism are not linked. In that case, I'll specify that the language and mythology are specifically what interest me.
This is a very common misconception that surrounds the phrase "conservative languages," because a connection is automatically (and quite understandably) made to cultural conservatism. Simply put, no correlation between linguistic and cultural conservatism has ever been found (as far as I am aware). A conservative language is a language in which very few "innovations," or changes in grammar/phonology/morphology/etc, are made. Icelandic, for example, is also a relatively conservative language, because it has retained many of the features of the language it and the rest of the Scandinavian languages are descended from, but Iceland is one of the most culturally progressive countries on earth. Perhaps there is more to be said in terms of the mythology, but as to the linguistic aspect of your question, nothing really "made it" like that.
hi, hopefully you'll get some help on this one, but FYI, you can get a start with this comment from /u/rusoved
While there are a lot of good answers here and in past threads, I'd recommend you go to /r/linguistics since they specialize in that