The overwhelming majority of the tax deals were/are available to other employers in the state as well. IIRC, only the land/building deal was specific and a version of that is likely to be available to whomever decides to build on the site.
https://www.citylab.com/life/2018/01/the-case-for-the-case-a...
I didn't actually read it, so I'm not sure how sound his argument is. Even if plausible, it's obviously just an article by a recent law grad and not actually the clear controlling law today.
Even if other companies were eligible for most of the deal, the fact that even a small part of it might have been specific to Amazon meant that the Foxconn story and fallout became a relevant part of the discussion