You downloaded a generic 6.1 package, not the one tailored to your Mac. Fix: Delete the downloaded package. Use Boot Camp Assistant’s “Download” function again. Each Mac model (MacBookPro11,4 vs iMac17,1) needs specific drivers.
Avoid generic "Driver Booster" or "Driver Download" sites. Only trust the files extracted from your own Mac or reputable archives like the boot camp 6.1 download