If they decided to compete with GPU, they would have just lost in gaming GPU sales to NVIDIA due to mindshare and they wouldn't have had the resources to develop the software to compete. And datacenter GPUs were still a niche and rare product.
AI/ML was not realistically something they could predict or bet the house on 7 years ago. And just like Lisa said in the recent presentation, AI is in its early stages and will be a growing and long term business venture.
Additionally, their CPU chiplet developments were critical in producing the talent and experience that would translate to GPU chiplets that AMD is not utilizing on RDNA 3 and CDNA 3, providing a strategic advantage over NVIDIA.
They still have the time to enter it with their MI300s AND now they have the money and resources to develop their software ecosystems more.
AMD absolutely made the right move to focus on Zen and HPC. It's not their fault that investors are blindly overhyped about AI.
AMD's greatest threat in datacenter AI hardware isn't even NVIDIA. It's the biggest tech companies producing their own AI hardware (Google, Meta, Tesla, Amazon) effectively and eventually eliminating the need for AMD or NVIDIA GPU/AI hardware.