Why is it past tense

Joaquin, 

In French, ‘historical’ articles are usually written in present tense, as if the events are happening with the reader and writer witnessing them as they occur. Past and future are relative to the ‘present’ being described.

In English past tense is usual for these types of articles and stories.

This difference is not reserved for ancient history, but also in narratives and biographies etc such as this. 

Hence you will often see a ‘tense shift’ when translating such articles to preserve the most appropriate tense of the respective languages.

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