Carl Schmitt did in fact made the jump, and he's one of the most read constitutional law writers in the last century. Not sure if Max Weber would have done the same, most probably not (he was really versed in English constitutional law, his "Economy and Society" has lots of quotes to Maitland's "History of English Law"), but he didn't strike me as a fervent supporter of democracy rights either.
And there was also the definite jump made by Heidegger, not exactly a legal scholar but a very well-read person nonetheless (and a mentor to Hannah Arendt, among others).
The germans you mention were certainly well-informed about foreign traditions, but their knowledge didn't create a living continuation of these traditions where they ended up.
(The context is, since it's been a few hours, was a claim that education was a way to circumvent this 50-year institutional forgetting, which I took to mean national institutions. And the counter-claim is that many places have good education and terrible institutions, why haven't they imported this ersatz institutional memory? If it works for local preservation, why doesn't it work for international transplanting? And I don't completely know, but the successful international knowledge grafts seem to be technical subjects. )
And an ironic situation, given his nazi ties and her jewishness...
Scholars deeply steeped in Bismark's thoughts & mistakes, or in English constitutional law, didn't make these jumps.