The Tesla plant has 10000 employees and reported 450 cases between May and December. Which is 4.5%.
There is no data for January/February/March, but this doesn't read like a big deal at all. Furthermore, there is no way to confirm that those 450 cases come from the Tesla factory itself.
If the journalist had wanted to write a convincing article he should cover other businesses and show that among those that stayed open, Tesla is an outlier in covid cases, that would prove that the reopening endangered the workers.
[1] https://www.latimes.com/projects/california-coronavirus-case...