Was anyone planning on building a data center in Maine in the next two years? Probably not, so all this amounts to is a meaningless law that politicians can say they worked hard on to ensure that the citizens of Maine were blah blah blah. Even though it did nothing expect it to be talked about excessively when the candidate is up for reelection. This is just a hot button issue that a lot of people are worried about or feel strongly about so it's easy to score points with voters with something that cost no political capital. It's the equivalent of passing a resolution to recognize cancer is bad, only it's less obvious what is being done to the average voter.
There have been several instances now of counties that have made local ordinances effectively banning data centers. I'm not sure if all of them were in counties where anyone was considering opening a data center, but it's not that much different than counties banning the sale of liquor. Sure, you or I might think it's stupid, but I also suspect that you might like at least some of the laws or regulations in place at various levels of government that should also be similarly done away with while letting the market sort it out.
The actual number of data centers that will be built is still small and even if some places want to ban them, somewhere else won't. To the extent that I think people should be able to outlaw things they don't like on property that isn't theirs, I am more receptive to it if it's a popular initiative than one pushed from higher up, but I think that even the people who agree in this specific case would find reasons to be upset if the state/county/whatever were banning something that they personally liked.