Comment by pjmlp

Yes, that is part of "it was too late".

OneAPI builds on top of SYSCL, is basically Intel's CUDA, which it is already the second attempt to have C++ in OpenCL, during OpenCL 2.x, an effort that worked so well, that OpenCL 3.0 is basically a reboot back to OpenCL 1.0.

Also even SYSCL only got a proper kick-off after CodePlay came up with its implementation, nowadays they sell oneAPI support and tooling, after being acquired by Intel.