Charles Ellicott Commentary Deuteronomy 8:20

"As the nations that Jehovah maketh to perish before you, so shall ye perish; because ye would not hearken unto the voice of Jehovah your God." — Deuteronomy 8:20 (ASV)

Because ye would not be obedient. — In return for your disobedience. The same word is employed in Deuteronomy 7:12. The use of the word in these two places might fairly be taken to mark off the intervening portion as a complete section of the discourse.