>Colonial conquest is not the primary methodology of linguistic propagation. Trade is.

A "primary methodology" only applies in "most" cases, not all of them.

Lots of languages have perished for outside forces other than trade -- the Hebrew wasn't abandoned because a better trade language came around, but because Israel was conquered and the locals scattered. Other languages were persecuted by decree. Others died because their native speakers were eliminated. And several other ways (e.g. Mussolini tried to smooth out local dialects of italian using the powers of government plus radio and early cinema).