Comment by yatopifo

I think there are two reasons. First, with AI, you get see intermediate successes and, in theory, can derive profit from them. ChatGPT may not be profitable right now but in the longer run, users will be paying whatever they have to pay for it because they are addicted to using it. So it makes sense to try and get as many users as you can into your ecosystem as early as possible even if that means losses. With fusion, you won't see profitability for a very very long time.

The second reason is by how much it's going to be better in the end. Fusion has to compete with hydro, nuclear, solar and wind. It makes exactly the same energy, so the upside is already capped unlike with AI which brings something disruptive.