How to create a product display view showing all users who purchased a product through a specific display
Your view needs to have this relationship setup, with multiple relationships added so you can relate your entities in this way.

Product Display > Product > Order > User

I should be able to provide a stronger answer if you can provide a little more detail, but have struggled with a similar view I had to create about 2 years ago and remember it taking a few days for me to resolve :)

Good luck!