Ha! I had in fact already formulated that obvious response to myself in my head, and mocked myself over it. But thanks for giving it concrete expression, and allowing me the opportunity to state more clearly what I was trying to say.
There are some of Russell's teachings that Rutherford was clearly never fond of, in particular the pyramidology. Rutherford downplayed it and eventually dropped it altogether.
But zionism is not such an obvious case. Rutherford didn't carry it forward reluctantly, he wholeheartedly embraced Zionism, as can be seen reading "Comfort for the Jews". And neither did Rutherford quietly drop Zionism, but he did a complete 180 and totally trashed Zionism in his later years.
So I wonder what made Rutherford re-evaluate and radically alter his position between 1925 and 1930. It's presented as simply a new consideration of the scriptures. Penton says it's because Rutherford was anti-Semitic and possibly had particular experience of Jews in Brooklyn. Was it simply either of those, a combination, or something else?