For the TRO to have been issued, would sandoz/mnta have had to show that the FDA made the wrong decision or would they have had to show that the FDA's decision was harmful to their business or both?
It would not be enough to show FDA made a wrong decision.
To get the injunction SNY would have to show irreparable harm and that the FDA's decision was “arbitrary, capricious, an abuse of discretion, or otherwise not in accordance with law.” 5 U.S.C. § 706(2)(A)
Not sure but I think the standard of proof in attacking an agency (FDA) is "clear and convincing".
Unless they have some "smoking gun" this is being done for other reasons such as effecting market shares.