Worth noting that they probably aren't tearing it down just to run power and fiber, since those lines can go under a parking lot without touching the building. The real issue is that a data center needs way more electrical capacity than an old Kmart ever had, so the dirt is worth more because of the substation and the transmission lines feeding it, not the site itself. Comps are also a nightmare because you can't just look at nearby retail leases or even regular industrial land, since the value is tied to power access and that changes block by block. Some assessors end up valuing these as special purpose properties, which basically means you build the value from the income the servers bring in instead of comparing it to anything else. So yeah, the lot being fenced off doesn't mean the building is doomed, it usually means the power upgrade is the whole point.