Bicycle Mechanics - rusty/corroded(?) small parts

Fasteners, washers, bushings & spoke nipples are all degrading. Anything made of steel. Comes w/age, I guess, but I try to take good care of it. I'm forced to replace the front brake cause it's actually locking up (rust inside). Did I do anything wrong? I realize components don't last forever.....

Ref: 2005 c'dale bad boy; maybe 17,000 miles; all original parts cept tires, pads, chain; I use q tips/hairdrier after a wet ride

Take the front brake off. Take it apart carefully & use wire brush, scraper & emery paper to remove corrosion away. You can use rust remover on the non aluminium parts. Reassemble with waterproof grease (even regular automotive grease is better than nothing) applied between the parts that move against one another, and on threads.

Voila, your brake will work like new.

Rebuilding a lot of less-expensive bikes like I do, I see this a lot. Better bikes have stainless fasteners, stainless cables, aluminum bits....All pretty resistant to rust.
With cheaper bikes, you get all-steel all the time. It rusts if left out after a while. I find a Dremel with wire-brush attachment is ideal for knocking this stuff off.
Bolts and nuts can be given a thin coat of grease, or WD-40 is a fair rust preventer.

I also forgot to say that the cables/housings will probably benefit from a change. Allowed to get too "crusty" these can ruin the response even of decent brakes in good working order.

The good news is that it can be fixed without resorting to new components