@galaxie
I generally agree with you, but I hold on to the ideology theory when I realized that the changing details of the religion is also an earmark of ideological groups.
A from of "confirmation bias" and denial create a means of bending or re-interpreting reality when reality starts intruding on ideologies. For instance, prior to the dropping of the atom bombs the belief in kamikaze (the spreading of the worship of the Japanese emperor) was a non-negotiable part of the invasions and war effort of Imperial Japan. But after the war began to turn in favor of their enemies, "new light" suggested that engaging in kamikaze could be limited to the Japanese people only without proving false to it and that the central principle behind kamikaze was the protection and preservation of the emperor and his divine status (it's a little more complex than this, but I am trying not to go so far off the subject and thus I am condensing things).
Japan tried to make peace based on this new interpretation of kamikaze, but the American government demanded full surrender, including that of the emperor. When the Japanese refused the atoms bombs came down. In the eyes of the Japanese the impossible happened: their "gospel," kamikaze, was declared false by the emperor himself when he announced the unconditional surrender of the Japanese on national radio, thus dissolving Shinto from a god-worshipping cult into a shell of mere customs that it has become today.
The central idea behind the Watchtower is really but one: they are the one true religion. If you go back to the 1870s and check their doctrines and practices from back then and compare them to what they are today, you will note that everything has basically changed but that one central view. They are an ideology with an impromptu theology designed to twist and turn every way to preserve the main illusion: that they are the one true religion.
They will disown Jesus and Jehovah before giving up that central belief.