Air is a very poor heat conductor, and among the best insulators. The thermal paste conducts the heat much more quickly. If it’s not touching maximum surface ar

Air is a very poor heat conductor, and among the best insulators. The thermal paste conducts the heat much more quickly. If it’s not touching maximum surface area on the things you want to conduct heat between, and the heat has to dissipate solely through the air that’s touching the processor, that’s much less effective at cooling.