Of course, these wannabe guys use the proper fraktur. They usually use the wrong s and don't care about proper ligatures.
"The rejection of modernism"
And many of them use Fraktur wrongly (in particular: wrong usage of long vs round s; not using compulsory ligatures).
not /s
Ostentatious religious behavior (such as public devotion) while ignoring quite a bit of the core message of Christ comes across as shallow. The clearest case is Trump, who has possibly broken all 10 commandments, and commits 6 out of 7 cardinal sins.
Now, associating that with all right-wing Christians is probably a generalization, but this image is not helped by their leaders, and the complete lack of visible opposition against them.
Using wrong letters and ligatures (in Fraktur) has barely anything to do with grammar; this is rather orthography.
You cannot argue with stupids
Also the modern far-right in Germany has an undercurrent of monarchists, we've just lost the political language to label them as such - much like how we unironically refer to conservatives as "centrists" because referring to anyone but a nazi as "right-wing" is often implied to have certain undertones, although the conservative party that helped pass the Enabling Act was literally called the Christian Center Party.
And although the Nazis weren't exactly ideologically coherent - fascists generally aren't - the driving ideology in the modern German far-right (including within the AfD) is actually völkisch nationalism which the Nazis were at least making heavy use of in their propaganda.
I'd even argue remnants of völkisch nationalism even made it into the German constitution: it uses the term Volk and Volkszugehöriger (in Art. 116 Abs. 1 GG) without defining either of them. The definition of Volk instead had to be provided by a constitutional court ruling - German citizens plus Volkszugehörige - and that second term is defined in a seperate law (§ 6 BVFG) which uses a very narrow and arbitrary definition that's clearly a condensed bureaucratic remnant of a much broader ideological pre-existing definition (arguably the consequence of having to deal with a similar problem as laws trying to combat racism that want to avoid validating "race science" by pinning down exact definitions for each relevant category)[0].
Also in German popular culture the colloquial definition of "Deutsch" seems to be very much colored by völkisch ideas: someone who is "ethnically distinct" (e.g. skin color, eye shape) is generally regarded as a "migrant"/"foreigner" even if they are German citizens, speak fluent German, are culturally German and have multiple generations of direct ancestors who lived in Germany.
[0] Source: Bundestag white paper "Zu den Begriffen „deutsches Volk“, „Deutsche“ und deutsche Volkszugehörigkeit“ im Grundgesetz":
https://www.bundestag.de/resource/blob/643190/7855da277bbd33...
References:
Art. 116 GG: https://www.gesetze-im-internet.de/gg/art_116.html
But that isn't quite what it says either. Pragmatic considerations may have given the decisive push, but it seems that Gothic script had always been in a precarious position on the faultline between the archaising and modernising instincts of Naziism. The specific tall story that was eventually presented about how it was Jewish was quite clearly a low-effort post-hoc justification, but it seems it was always quite easy to take an anti-Fraktur stance from a Nazi perspective: see A. Hiedler, op. cit. And even just going on the small extract provided from that Reichstag speech https://penelope.uchicago.edu/encyclopaedia_romana/luftwaffe... , it seems that Hitler's objections weren't just pragmatic: before he gives a practical reason to drop Fraktur, he attacks Gothic revivalism in general on aesthetic grounds, no small matter to the Nazis. My assumption is that his objection to Gothic revivalism was based partly on a general aesthetic instinct that too much revivalism is cosplay and naff; and partly on a disapproval of medieval Germany specifically as a model or claimed precursor for Nazi Germany, for various reasons. A possible third, type-specific, factor, mentioned in https://penelope.uchicago.edu/encyclopaedia_romana/luftwaffe... , is that compared to "Atiqua" "Fraktur" looks vaguely kinda more Hebrew-ish. That could plausibly have been the underlying sentiment behind the (apparently completely false and baseless https://worldcrunch.com/culture-society/nazi-typeface-fraktu... ) story spun about Jewish printers in Schwabach.
A lot of things boiled down to post-hoc ideological justifications for the personal preferences of Hitler and his ilk. Even the racism was incoherent - it's cliché to point this out but Hitler himself infamously looked nothing like an Aryan übermensch despite the Führer cult treating him akin to a divine figure. This is consistent with research indicating disgust as a strong motivating signal in right-wing politics.
I'm almost hundred percent sure I've seen Mein Kampf seen set in Schwabacher which was printed while Hitler was still alive, but I'm not sure on the exact year. I'm also certain I've seen Hanns Johst's plays posters set in (stylized) Fractur. I'm sure you can find the Nibelungen posters with the same kind of (stylized) font from that time.
So, at least in the way things are presented in Kapr's book, and I think it was understood that way even before him, Fractur has much to do with the development of printing, especially the part where individual letters were reused (early printing used to etch the entire page at once). Germans would have a reason to be sentimental about that font because, after all, they were the inventors of this kind of printing. I could see how this would be in line with nationalism.
Similar, for example, in Russia, the stylized variant of pre-Peter I (a.k.a. "early Cyrillic" or "church-Cyrillic") is still a popular choice for all sorts of nationalist propaganda posters, even though it was replaced in the late 16 hundreds.
Similar, in Ukraine, there are fonts that strongly associate with nationalism, eg. https://en.wikipedia.org/wiki/Ukrainian_skoropys and Georgij Narbut's font: https://luc.devroye.org/fonts-86142.html even though they are impractical and aren't used for everyday tasks.
In Hebrew, there's Hayim font, that strongly associates with the Zionism / Socialism movement of the pre-declaration of independence and soon after, but the font otherwise isn't very useful for modern everyday needs.
* * *
Bottom line: I don't think Nazis represent the whole spectrum of nationalism. On the other hand, nationalism will find and glorify original local developments, in typography just like in any other field.
My reading of Nazis is that nationalism wasn't their main goal. Their appeal was "law and order at any cost", "removing impediments to prosperity, whatever they may be" much more so than digging up historical relics confirming the eternal greatness of Aryan people. Textbook nationalists are rarely expansionists: they may be hostile to their neighbors having claims to some historically contested territory, but they don't normally launch conquest of far-away lands. The later seems to be more of a thing of people with more universal ideologues.