There absolutely were hordes of evangelists touting this or that tech company (including google, redhat, amazon etc as well as pets.com and a bunch of others who didn't survive) saying in 5-10years these were companies would be the biggest thing since sliced bread. In some cases they were right.
The VC money is betting on a similar sort of monopolistic dynamic occurring in the AI space. They're not saying that 100s of billions of dollars of value is going to accrue to openAI because of chatGPT they're saying 100s of billions of dollars of value is going to accrue in the space and the most likely outcome is that the vast majority of that is going to be siphoned up by a couple of behemoths. Other than the incumbents (Microsoft, Google) OpenAI seems best positioned at the moment and whoever else creates breakthroughts will probably be acquired anyway just like instagram got bought out by facebook as soon as they got large enough to matter.