1) All the manufacturers write drivers for Windows if needed. They know the hardware, and so the drivers will be quick. 2) Most of the manufacturers write drivers for Linux. Often when they don't, they give the full specs to a developer and pay them to write the driver. 3) OpenBSD prioritizes security and correctness over speed. Windows/Linux do not. 4) Pretty much no manufacturers write drivers for OpenBSD. Generally it's one of the developers. 5) Specs are not always available. (Sometimes seldom). Often developers have to figure out how the device works by looking at what Linux does in their code.

So in general, if you ask "My hardware is faster on Linux/Windows, what is wrong?" The answer is: nothing. Nothing is wrong.

It's perhaps better to ask if there are things one could do to make it run faster.