Re: Iceland
The low outside temperatures make cooling far easier than (for example) a datacenter located in Arizona.
Iceland has experienced temperatures high enough to require active chillers: https://www.plantmaps.com/en/is/climate/extremes/c/iceland-record-high-low-temperatures
So you'll still need to pay for that capacity, and maintenance of the units, which is much more difficult to do where the condenser coils frequently get iced-up, snowed over, etc. Unless you're Google, and can just shut off entire data centers.
There's a lot to be said for building data centers in deserts. Lots of unoccupied open land, efficient cooling with evaporation, ideal for on-site solar panels, few or no blizzards or ice storms (which have a habit of taking down electrical grids and make it difficult for personnel to come and go), etc.
More on-topic, nuclear power generation hasn't proven to be price-competitive with wind and solar, and data centers are a terribly competitive business where even slightly higher electrical rates raising their costs is very likely to cause customers to go elsewhere.
A lot of datacenter activities (eg AI training) can easily tolerate the additional few milliseconds latency for the data transfer from Iceland to mainland Europe or the US.
It's a logistical issue, though... How long does it take to ship parts? How difficult is it to get people on-site for occasional major moves/reconfiguration/etc. The added expense of trans-Atlantic rush shipping and costs for remote-hands could easily eliminate any savings from the lower electrical prices. Of course huge companies can make the logistics work, but most cannot.