Conversation so far:
What was Edward Sapir moving on with?
Edward Sapir was now more preoccupied with testing hypotheses about historical relationships between the Na-Dene languages than with documenting endangered languages, in effect becoming a theoretician.
Are there interesting aspects to Edward Sapir becoming a linguistic theoretician?
During his period in Canada, Edward Sapir came into his own as the leading figure in linguistics in North America.

Question: How did he do that?
Self-contained rewrite: How did Edward Sapir come into his own as the leading figure in linguistics in North America?