I think it was not a matter of raw power. It just didn’t deliver sufficient amperage on the PCIe rails.
CX series is the entry level of corsair. They don’t build their power supplies. The high-end product are built by Seasonic, Fortron, SuperFlower, etc.
The low-end series are built by way less renown manfacturers, with crappy components.
With V1000 you bought one of the best kilowatt on the market (but a Corsair RM/AX would have been just fine).