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Religion can and does preserve memes and linguistics, but only trade can scale it out.If it was just for trade, language learning would be relegated to merchants in those countries and few others.
Government, bureaucracy and occupation matters more than trade in this regard. That's how latin become the norm in a large area during the roman empire -- and not because everybody in those regions traded directly with Romans or couldn't agree on pricing otherwise.
Same e.g. for French -- it's not because of trade they got big as a language in the 18-early 20th centuries, but because the french run a big colonial empire.
And English, beyond trade, were the language of the big British colonial empire, and afterwards of the dominant culturally power that was America (Hollywood, rock, pop culture etc.).