It would generally be the opposite, what law gives them standing to sue?

My knowledge as a non-lawyer generally agrees with above, most states won’t allow you to sue for neighbors doing something legal that decreases your property value (CA is the exception I’m aware of, and even then it’s a “sometimes” kind of thing).

I’m not even sure who they’d sue. Presuming the land is zoned for a datacenter, the datacenter is allowed to do datacenter things. You could sue the city to try to prevent the zoning, but sovereign immunity would preclude suing them for doing their job (zoning, in this case).

According to https://en.wikipedia.org/wiki/Standing_(law) the requirements for standing were developed in the Constitution and elaborated in some later cases. To quote from the article, the apt criteria seem to me (2 of the 3):

1. Injury-in-fact: The plaintiff must have suffered or imminently will suffer injury—an invasion of a legally protected interest that is (a) concrete and particularized, and (b) actual or imminent (that is, neither conjectural nor hypothetical; not abstract).[44][45] The injury can be either economic, non-economic, or both.

2. Causation: There must be a causal connection between the injury and the conduct complained of, so that the injury is fairly traceable to the challenged action of the defendant and not the result of the independent action of some third party who is not before the court.[46] ---

The best way to understand why standing was not found is to read the court's ruling. Unfortunately (but not unusually) 404Media has not linked to the judgement. (I will try to find it.) My guess (IANAL) is the injury is hypothetical or conjectural.

It would be even worse for city planners if anyone could sue for a reduction in their property values due to a decision they made.

There isn't a single precedent; standing and jurisdiction are like 70% of civil procedure in law school. This page is a good jumping off point: https://www.law.cornell.edu/wex/standing

Lots of questions about the colloquial (mis)understading of standing, and the actual standard, so might as well reply here.

IAAL, and the legal precedent is... the doctrine of standing. The article is paywalled halfway down for me, so I don't know the particulars of the complaint, but it's presumably in state court. Either way, most state doctrines are some variant of the essential elements for Article III (federal) standing, which are 1) An injury in fact that has or will imminently occur (i.e., no speculative or indefinite injury); 2) That injury must be a direct consequence (but-for causation) of the defendant's actions or inactions; 3) The injury must be redressable by the court. "Soandso did something and I, an otherwise unconnected party, may potentially lose value on my home's resale value at some undefined point in time in the future" is the type of abstract, speculative injury that never clears the hurdle. To the extent you actually want to soak in the torment of 1Ls everywhere, Lujan v. Defenders of Wildlife and TransUnion LLC v. Ramirez are your big ones.

Outside of that, you'd likely need standing created by statute to bring a claim. But standing is just a threshold question that every litigator with a brain will attack because it kills the whole thing before reaching the merits. Even if Ps had standing, the prospects of prevailing aren't great given the timing, parties, and issues involved.