How does cleaning your ears improve hearing?

Cleaning your nose, like blowing it out and using a saline rinse in it helps to get rid of excess mucus and also moistens it so it stays healthy. Clogged noses can clog ear tubes too because the two have a connection. When your nose is stuffy, chances are your ears are plugged. Sinus drainage can cause nose infections and ear aches too so keeping your nose clean, literally, is helpfrul for prevention of both.

When one doesn't rinse their nose out and keep it blown, infection can easily build up in the sinus cavitiies. This can cause a sinus infection which is sure to affect both the nose and the ears. It is indeed miserable.
When your nose and your ears are clean and free of being clogged, you can breathe easier and hear better too. They just go hand in hand like that.