Is “concessions they didn’t ask for” weird? That seems like normal bidding in a competitive market.
Yes, it's weird. It's just a right wing anti-environmental tactic. In order to permanently circumvent some environmental protection they don't like (clean air, clean water, endangered species) they make a deal with some private entity and then years down the road they throw up their hands and say "there's nothing we can do about it because of this contract." Because contracts are enshrined in Article I of the Constitution, they have a strong case. It's really bad that people can be held in perpetuity to the terms of a contract made by a single bad mayor or governor, but that's American jurisprudence for you.
It is blatantly false to claim that a mayor can circumvent the EPA or any state level environmental agency by simply signig a contract. That's not how anything works...
With a company as big as foxxconn, the federal government is in on the deal too
It's quite demonstrably true that contracts have been used to constrain government action over and over again in US history. See for example Reclamation water contracts in the west vs. all manner of conservation laws.
The reclamation water contracts are not an example of a mayor circumventing existing federal or state environmental regulations - they are a completely different thing. I'm not even sure where you'd draw the parallel other than it contains the words 'environment' and 'contract'.
But contracts aren't supposed to have provisions in them that are against the law.