My only guess is they have a parallel skunkworks working on the same thing, but in a way that they can keep it closed-source - that this was a hedge they think they no longer need, and they are missing the forest for the trees on the benefits of cross-pollination and open source ethos to their business.
Do you expect them to be able to capitalize on the AI fad so much (and quickly enough!) that it's worth dropping the ball on projects they're now doing well in? Or perhaps continue investing into the part of the market where they're doing much better than nVidia?
They very much plan to compete in this space, and hope to ship $3.5B of these chips in the next year. Small compared to Nvidia's revenues of $59B (includes both consumer and data centre), but AMD hopes to match them. It's too big a market to ignore, and they have the hardware chops to match Nvidia. What they lack is software, and it's unclear if they'll ever figure that out.