It seems out of character for a German patriot like Wagner to stage such a Germanic Opera in France….even more out of character is that he reworked the opera and added a ballet to suit his Parisian audience.

Tannhäuser und der Sängerkrieg auf Wartburg
Upon researching this event, I learned that Wagner was in Paris because he was exiled from Germany for almost 13 years, from 1849 until 1862. Earlier in his life, Wagner was somewhat liberal and a revolutionary. He lived and worked in many places, often moving around to avoid creditors, but during the time of socialist uprisings that spread across Germany in 1848, Wagner lived in Saxony. It was in Dresden that he played a minor supporting role in the unsuccessful May 1849 Uprising. After the revolution failed, warrants were issued for the revolutionaries’ arrest. Wagner had to flee, first visiting Paris, then settling in Zürich, then in Venice and finally back to Paris and the premiere of Tannhäuser.

The political ban that had been placed on Wagner after he fled Dresden was fully lifted in 1862. Wagner returned to Germany and wrote a number of articles in his later years, often on political topics, and often reactionary in tone, repudiating some of his earlier, more liberal, views.
In case you are wondering, Tannhäuser …full title Tannhäuser und der Sängerkrieg auf Wartburg (Tannhäuser and the Singers’ Contest at Wartburg Castle)… was originally an 1845 opera in three acts, with music and text by Richard Wagner. For his 1861 Paris premiere he reworked the opera and added a ballet to suit his Parisian audience.
The opera was based on two German legends: Tannhäuser the legendary medieval German Knight and Minnesänger, whose poetry appeared between 1245 and 1265… and that of the Wartburg Song Contest which involved a knight named Heinrich von Ofterdingen, said to have taken place around 1207.

Tannhäuser the legendary medieval German Knight and Minnesänger

The plot also merges the historically real Tannhäuser with the myth of Venus and her subterranean realm of Venusberg (mountain of Venus). Thus half of the opera takes place in a historical setting, and half takes place in the mythological Venusberg.