We have a bunch of brands that are no longer available and we have no intention of having inventory for these brands again. I looked in Store Manager and none of these vendors have any products assigned to them but the pages are still there. Just to be clear, I'm not seeing the brand in the menu but I see people are getting there by looking at Google Analytics.
How do I get the pages for these brands redirected to the homepage?
If you Delete the brand in Store Manager the page will automatically be directed to the homepage. You can delete these brands by going to Products > Catalog > Categories and selecting the Category (Brand) you want to delete. At the top of the page you'll see a Delete button. Click on it and confirm the Delete. That's it!
The same applies to deleting Departments and redirecting those back to the homepage.