I have one keyboard plugged in, but 4 different
HID Keyboard Device are shown. Why?
Why not? ;-)
Keyboards (or other input devices) use multiple HID devices for various reasons. On keyboards, multiple devices are often used to make N-key rollover possible without relying on better HID support.
Keyboards are not the only type of input device that present themselves as keyboards. Mouses also often do, especially if capable of keyboard macros.
For example, consider the following:
From top to bottom, it’s a “Das Keyboard” keyboard, a Logitech MX518 mouse and a Logitech G900 mouse. All of them present a keyboard.