Today, we’re announcing that Amazon will invest up to $4 billion in Anthropic. The agreement is part of a broader collaboration to develop reliable and high-performing foundation models.
(Thread continues from there with more details -- seems like a notable major development!)
It seems more likely to me that they would have gotten started anyway once ChatGPT came out. Although I was interpreting the counterfactual as being if Anthropic had declined to partner with Amazon, rather than if Anthropic had not existed.