Naturalism en.m.wikipedia.org/wiki/Naturalism and Bilogism en.m.wikipedia.org/wiki/Biological_determinism were a relevent movement in Germany in the late 19th and early 20th centuary. And for parts of the “Lebensreform” Bewegung en.m.wikipedia.org/wiki/Lebensreform it was en vogue to be vegetarian or vegan. It was not a totally fascist movement, but some members were hard core racist and ableistic. The NSDAP claimed some of their values, and formed it into their own propaganda. FE:

• Fkk into nazi body cult a la Leni Riefenstahl
• Healthy, natural lifestyle in general into an arian, healthy lifestyle for a society ready to fight
• esoteric views into their own arian pseudo-religion

So as part of this, hitler was a propagandizing vegetarian. And Hitler and other leading nazis were some kind of “animal rights activist” …wikipedia.org/…/Animal_welfare_in_Nazi_Germany

Some of this values are deeply printed into the NSDAP and are so part of today Nazis in Germany. “Nazi-Hippies” (as people in my bubble are caling them), are still a thing here.

As far as i remeber, the German Green Party had in the founding times problems with Nazis in the party.

If you want better sources, i can only give you german Documentaries from arte or dlf. Im just an interessted dude and not a historian or teacher. Im not prepared to present sources in English :)