What are the terms? It is not at all clear from the announcement. "part of this three-year licensing agreement", it _could_ mean the license cost is $1 billion, which Disney in turn invests in OpenAI in return for equity, and they're calling it "investment" (that's what's hypothesized above, but I don't think we know). Disney surely gets something for the license other than the privilege of buying $1 billion in OpenAI stock at their most recent valuation price.
Disney gets the opportunity to tell the board and investors that they are now partnered with a leading AI company. In effect, Disney is now an AI company as well. They haven't really done anything, but if anyone asks they can just say "of course we're at the forefront of the entertainment industry. We're already leveraging AI in our partnerships"