Most of the people pursued in these "AI talent wars" are folks deeply involved in training or developing infrastructure for training LLMs at whatever level is currently state-of-the-art. Due to the resources required for projects that can provide this sort of experience, the pool of folks with this experience is limited to those with significant clout in orgs with money to burn on LLM projects. These people are expensive to hire, and can kind of run through a loop of jumping from company to company in an upward compensation spiral.

Ie, the skills aren't particularly complicated in principle, but the conditions needed to acquire them aren't widely available, so the pool of people with the skills is limited.