ATF, your theory makes perfect sense. On the other hand it's worth noting that Ratzinger was quite liberal to begin with, especially during the Council where he was a member of the progressive wing. Also, the first draft of his postdoctoral thesis was even rejected for being "dangerously modernist". All this changed only after he witnessed the 1968 student protests  during his tenure at the Tübingen university which apparently traumatised him so much that he practically fled to Regensburg. From then on he seems to have steadily become more conservative both in his theology and of course later in the way he shaped his papacy.