Why did God allow the Assyrians to take Israel captive?
Israel had reached the point where God put them out of His mind, so He permitted the Assyrians to come down and take them captive. The stated reason is therefore God's permission, rather than Assyria acting independently. Their conquest happened because God allowed it after Israel came to that condition.
Les teaches that Israel had come to the place where God simply put them out of His mind. Because of that, He permitted the Assyrians to come down and take them captive. Les pauses there to warn about much false teaching attached to this subject, and he also recalls his earlier comments about satanic powers in high places. He mentions receiving the Biblical Archaeological Review and an article that illustrated what he had been saying, which he plans to share in the next program. The broader point is that people should study God's Word rather than ridicule it.