Why does OpenAI need so much more compute than everybody else? DeepSeek, Qwen and many others build competitive models that need much less capital.
That said, Alibaba not releasing the weights for Qwen3-Max and announcing $53 billion in AI infrastructure spending https://www.reuters.com/world/china/alibaba-launches-qwen3-m... suggests that they think they're now at a point where it makes sense to scale up. (The Reuters article mentions data centers in several countries, which I assume also helps work around high GPU prices in China.)
Circling back to OpenAI: I don't think they're spending so much on infrastructure just because they want to train bigger models on more data, but moreso because they want to serve those bigger models to more customers using their services more intensively.