You upgraded your graphics card. In the process, you also eliminated one of the reasons the graphics card was holding the cpu back. If the cpu can now run freely the cpu cooler can spin up.
Is it possible that in the psu exchange process, the cpu cooler got unseated? Can you check the cpu temperatures?
right now im reading the temps with cpuid hwmonitor and for temps as of this second on my cores for min are in this order 44c 41c 41c 44c max 58c 55c 54c 56c and under where it says the motherboard or whatever (where it says voltages and then temperatures) 26c 86c 50c 26c for min and max 40c 104c 57c and 40c with the fan speed for the main one at 1369rpm min and max 2626rpm
the gpu's stats for tempetures are min 46c and max 81c for its fans it has 1500rpm min and 2340rpm max