Heating issue with RPi4

Why does my raspberry pi 4 heat when cpu load is below 10%. The frequency goes from max to minimum. When it goes max the heating starts, fan for cooling comes on. I setup cooling thermostat on gpios. Thought I am using the raspberry pi aluminum cooling blocks it is not helpful. The fan which comes with the heatsink gets damaged due to heat so I used another fan to blow out heat.

I am not running any big processes on the raspberry pi. Only a supervised homeassistant installation.