I haven't built a new gaming PC in a long time, but with the coming EOL date for Windows 10, I find myself trying to get up to the date on the latest when it comes to building PCs. An interesting topic I ran into, is how to setup airflow on a PC Case. Specifically, having too many fans at the top of the case, can actually be harmful to your CPU in the long run. The reason seems to be fairly simple, but only when you can visualize the airflow, as the presenter does in the following video.

So in a nutshell, too many top case fans can pull the air out of the PC case, before that air is even allowed to pass through CPU and motherboard.