But these CPUs did not really gain a foothold in the market from the very beginning
Intel has removed support for its Xeon Phi Knights Mill and Knights Landing accelerators from the LLVM/Clang 19 compiler, which effectively means the end of support for any kind of MIC architecture.
Knights Mill processors experienced numerous lags back in the day and were reported to miss performance targets. Once upon a time it was planned to build the Aurora supercomputer on them. Due to these same problems and delays, the project was switched to Sapphire Rapids processors and Ponte Vecchio GPUs, which allowed Aurora to become the world's second Exascale supercomputer. True, there were also problems with the new components in the form of long delays, and the energy efficiency of Aurora was ultimately far from the best.
Since the beginning of this year, support for Xeon Phi Knights Mill and Knights Landing has been deprecated in LLVM/Clang 18. Now in the release of LLVM 19, which will be released around September, support has been removed completely.