But if the traffic to SO is reduced significantly because of Google, there will be a death spiral. There wouldn't be a site to go and ask new questions, and even if the site is still there, nobody will bother to answer. The core problem is that the people who create the new knowledge (the answer writers) and the people who aggregate the knowledge (StackOverflow) will not get any concrete return for their efforts, since they are cut out of the consumption loop.

You don't need to be a big business like SO to provide this service. The death spiral would only make sense for a business with demands for growth out pacing the market, so they exit. or who has an operation which is too expensive vs the ad revenue.

But that doesn't mean other businesses can't fill that reduced role more efficiently.

You need to be a place that people go to ask and answer these questions. It doesn’t matter how big or small you are if you don’t exist because the people answering the questions don’t go to you in the first place. You’re right that there’s another means in which a business can fill this, but I don’t think it’ll be stack overflow.