It's likely the GPU boards are designed for water cooled data center racks and might not fit in a regular PC case. It's also possible the PCB the GPU's are mounted to might not be standard PCIe cards that fit into an ATX case.

I bought a used NEC SX Aurora TSUBASA (PCIe x16 board that looks like a GPU board) and realized it has no fans. The server case it is designed to fit into is pressurized by fans forcing air through eight cards on a special 4 + 4 slot motherboard. I have to stack and mount three 40mm fans on the back.