The problem with OneAPI is naming. It leads people to believe that is another competing standard where in fact is is simply just an implementation of a standard compliant SYCL compiler. If it just had been named “Intel SYCL compiler”, similar to the existing and accepted Intel OpenCL compiler, it would have been easier.
What would you expect the hardware consortium to coordinate on? Unified ISA?
They were maintained by Codeplay - paid for my Intel. Nvidia can make contributions anytime they want, and here is the problem: Nvidia does not want to. Until each vendor starts pitching in with contributing their backend to an open standard, you will have to rely on others doing it for them.