He has spoken about it in other articles too, in Finnish media, and the gist that I got has always been that Minnesota is "Mikko's team", and he's not going there to mess it up.
Saku jätti Minnesotan Mikon haltuun via google translate, can't find the original Globe and Mail article right now
Also, Saku is 9 years senior to Mikko, so at some point it was to be expected that Saku's game would fall and Saku would indeed be in Mikko's shadow then, but good luck with getting a pro athlete and big brother to actually admit that.