I am aware that probably we have tons of examples of racist theories that do not put the Germanic peoples in the top. However, I find it remarkable that most of the proponents of scientific racism in the 18th and 19th centuries perceived the Germanic peoples as being superior to others.
And that is not the case, necessarily, of Germanic "scientists". We have for instance Henri de Boulainvilliers, a Frenchman, who proposed that the Germanic nobility of France was superior to the Celtic population. The usual "whites are superior" doesn't apply here, since Gauls are also white. He somehow perceived Germanic as being superior to Celtic.
Another example somewhat related is the perception of German racists of the Scandinavians as somewhat superior to themselves. This view was probably related to the fact that the North Germanic peoples were the least influenced by the Latins (linguistically and culturally speaking) among the Germanic peoples that survived (excluding east Germanic). This can be visualised here (Taken from an excellent answer by LangLangC in this question:
To which race do Europe’s peoples belong?
The peoples of Europe do not belong to a particular race, but are rather a racial mixture. Our German people is comprised primarily of six races.
And what are they?
The Nordic, the Pfalzish (fälische), the Western (westliche) the East Baltic (ostbaltische), the Ostic (ostische), and the Dinarish (dinarische) races.
The German people is, along with the English, Danish, Norwegian, and Swedish, the most racially pure of the European peoples. With regards to the purity of language, the Scandinavian peoples are in first place.
Werner May, Deutscher National-Katechismus 2nd edition (Breslau: Verlag von Heinrich Handel, 1934), pp. 22-26. (Quoted here: The German National Catechism)
Another interesting example is when the Brazilian government, in the 19th century looking for immigrants, placed Germans and Austrians on the top of the list, even though the Brazilian government was made of people of Portuguese stock (including the royal family itself). This can be found in the Imperial decree 5.663 in 1873. Unfortunately, I could find the info in the Portuguese Wikipedia article regarding the Italian colonization of Brazil, which states that:
Como exemplo, no decreto 5.663, de 1873, celebrado pelo governo imperial com Joaquim Caetano Pinto Júnior, no topo da lista apareciam alemães e austríacos, portugueses e espanhóis foram excluídos, mas incluía bascos e italianos do Norte [...] Por muitas décadas os alemães permaneceram no topo da preferência entre os imigrantes, por sua "índole" e seu "pendor" agrícola.
Which translates to:
For instance, in the decree 5663 in 1873, celebrated by the Imperial Government with Joaquim Caetano Pinto Júnior, the list was headed by Germans and Austrians, with Portuguese and Spanish being excluded, despite the fact that Basques and North-Italians were allowed [...] The germans stood on top of the preferred immigrants list for many decades, due to their "nature" and their agricultural "inclination".
My question is if there is some sort of a reason for this pattern, or if it is really just coincidence. I find it unusual, since my intuition would lead me to believe that the racists of each nation would perceive themselves as the superiors. It seems it is not the case. Why the bias towards the Germanic?