Griffin makes Mac accessories, and has for 15 years. Griffin’s customer base, and all of their sales/support/development expertise is focused on the Mac (and later iOS) ecosystem. It’s possible they could also market devices to Windows users, but it would take a lot of extra work on their part: market research to figure out what products Windows users would buy, lots of development effort including hiring Windows developers to write new device drivers, setting up new sales channels, retraining all their support staff.
Saying “there goes 80% of your market” is a completely uninformed statement, and all the folks in here pretending that it would be trivial for them to add Windows support are just delusional.
Plenty of other companies make hardware accessories for Windows computers, many of which have been Windows-only for decades.