You're saying the data center has a small footprint, but it does not. You don't need that much stormwater pond if you don't have giant impervious surfaces.
Deal sweetener is footprint (buildings, parking lots, and substation) being 1/6 of the land with the other 5/6 dedicated to nature preservation.
Not all wide open space is created equal. If it's wide open space with Eurasian grasses that get cut every few weeks, it's useless and has 0 benefit to the local ecology. Even if they weren't cut, they're still do very little for the ecology in the area.
If those forests don't have keystone tree species, then it's the same.
The people running these companies are so incompetent, they can't even do greenwashng right.
https://www.google.com/maps/search/Walmart+Distribution+Cent...
Even then, it is improper to assume anything about the stormwater management needs of one site based on another unrelated site. But even then, Walmart's site seems to be completely surrounded by stormwater management. Even the northwest corner of the site is a detention basin. [0]
The most obvious and logical conclusion to be made here is that an engineer told Microsoft they needed to have stormwater management of that size, so that's what they put in their plans. No sweetness, just lawsuit prevention.
If they want to be sweet, they should be building huge nature preserves (and they have enough money to afford it) into these plans instead of trying to be greedy by building the largest possible structures (they think) they can get away with.
[0]: https://beacon.schneidercorp.com/Application.aspx?App=DodgeC...