About a month ago my grandfather gave me the okay to work on a pi-hole and attach it to the router

So I did that yesterday, and he yells at me for it (because having a civil conversation is impossible with him) and says that we don't need "extra stuff" and says that I'll break the router.

I tried to explain how the process works but I was just shut down and interrupted.

He could have at least told me he changed his mind so I wouldn't have wasted over two hours of my day building and troubleshooting the device.

Mind you, he literally worked in hardware for 50 years and has had ham radio as a hobby for over sixty.