Imparfait? Why are you using devient?

You'll notice that the entire paragraph and following ones are in present tense. This is a stylistic means to draw the reader into the story. The same is possible in English as well, by the way, even if not used as commonly as in French.

That there is a  difference in approaches to 'tense' in writing formal historical articles between French and English is noted in the text preceding the article, and a link to the more detailed description is given: 

https://www.lawlessfrench.com/grammar/historical-tenses/