That'd probably make more sense if there wasn't also 50 other tech companies buying up RAM for the same reason (a sudden huge spike in demand due to AI taking off).
It's about volume, not a naive count of consumers. Article claims that OpenAI holds contracts for 40% of world DRAM production. That's just really obviously manipulation if they can't actually power those chips, come on.
They mean to resell them in a different form: as part of their PaaS or SaaS. Per the article, OpenAI is just hoarding the wafers, not purchasing the final product.