We do have cheap energy (from nuclear and mostly renewable CHP), cheap cooling, availability of educated workforce and stable state. And good network connections to Russia in addition to Nordic and Baltic states and continental Europe.
But latency to Russia and Baltic states isn't that different from where Hetzner already is. I just try to understand why people would choose Hetzner's new DC in Finland over that in Germany unless they offer cheaper prices there.
Otherwise I fail to see why Finland makes sense, unless you need cheaper energy for applications that don't need low latency.