How can Wilson Audio speakers sound that good if they are using OEM drivers?

BS in OEM land.

Aside from the obvious logical errors in this post I just want to explain something the OP fails to understand:

The worst Wilson sounds better than the best B&W

This is indisputable.

Aerial Acoustics has never produced their "own" driver either and yet has managed to create some amazing speakers. 

never mind any of those box speakers, the answer is that they do NOT sound that good, imhop, a box is a box! 

The new AkG  Klipshorn from Klipsch for 14k will fill a room with music like a live venue, and according to the guys selling 300k horn loaded systems at the Munich Show, they "are the best kept secret" in hi end and give you 80-90 per cent of  the sound of those systems..It is like a cross between best planar and best box speakers, but much better bass and dynamics, and emotional engagement with the music..btw, at 105 db, you can drive them with a clock radio! I have been at this audio thing for 40 years, they just kill everything out there!  

Sure soundwise if all you want is volume and are not interested in an image they are fabulous. Sixty years ago the most powerful amplifier made was 70-75 watts/ch and you needed something like the K horn if you wanted to attain realistic levels.