There are certain elements on the MOBO which need fixing with a certain paste. It’s heat-proof stuff.
I will get more info on Thursday (Not in workplace on Wednesday) and post it here.

Thermal paste between the CPU and the MB. a thin layer no thicker than a sheet of good A4 paper!

Burning out the motherboard I doubt is the lack of thermal paste IMHO, Case heat being the most likely culprit. I have no fewer than four fans supplying cool air from outside while another four exhaust hot air from the case.

It is all about airflow over components. Badly run cables will cause heat to linger if they are blocking airflow. The same as dust build up in an older machine.