It’s exceedingly unlikely that any of the people who were working on YC startups previously have any real professional experience with any of the following: slurm, collectives, NUMA systems, RDMA, compilers, systems programming, general HPC performance estimation or measurement, CUDA or ROCM or any kind of GPGPU/accelerated computing. But that is the core business of both of these companies.
I’m not surprised that these companies are well funded and hiring a lot of people. I’m surprised that they chose to hire the people who were previously making “Uber but for dogs” gimmick apps and not just hollowing out the HPC specialists from national labs.