PC CPU fan spins for split second

Hi, I have a PC I built about 4 yrs ago, Ryzen 7 3700x, 16GB ram, RX580 GPU.

A week ago I got to my PC and it was dead, replaced power supply as I found a blown component in the PSU, then the CPU fan just spins a split second and nothing, no LEDs, D-E-D DEAD!!! Replaced MB and RAM, still same issue.

Now I am left with either the CPU or the GPU, which would be the most likely suspect in your opinion?