Half of them are from India or China. Racial diversity is known to be detrimental to unionization. In fact, Amazon used this exact strategy to bust nascent Somali unions.

https://www.computerweekly.com/news/252481961/Amazons-Whole-...

Here is the obligatory scientific paper for those who cannot observe simple facts without a statistical analysis:

https://www.sciencedirect.com/science/article/abs/pii/S01762...