I think they're betting that as NVIDIA hardware gets more expensive and harder to get, especially in the datacenter, there's now an opportunity to entice developers to take on the pain of porting to HIP/ROCm.
Nobody cares about "users" in this case, it's bespoke applications running on bespoke infrastructure at scale.
AMD is just as fabless as NVIDIA, both compete for production capacity, and eventually TSMC etc will get around to producing more chips than the market will want to buy.
Nobody cares about "users" in this case, it's bespoke applications running on bespoke infrastructure at scale.