Do religious texts keep languages from changing too fast to understand each other? or?

Question

do they just give those in power a long-range playing field to change the useage/meaning of words to fit their agendas?

Answer 1

Neither.

Religious texts don't change, but the languages around them still do nonetheless. This is why religious speech is often noticeably archaic.

As to changing usage/meaning... that has nothing to do with the evolution of languages and everything to do with the willingness of parties with an agenda to uphold to twist and bend the texts to fit their needs. Actually, such parties have been known to delete, modify or rewrite passages when mere reinterpretation of the preexisting texts proved infeasible.

Answer 2

Anyone can change the usage/meaning of words to fit their agenda, but I can't imagine religious leaders sitting down and discussing whether or not the texts will be understood, or whether or not the vernacular will change.

I think it's more or less the purveyors of the message that twist and turn it to their advantage, not necessarily the ones that publish, or write said texts...