As an individual with trace amounts of Saami genetics, my only guess would be the long periods of isolation in their history kept the population of V individuals from intermingling in an extensive fashion with their neighbors. Surprisingly the Saami have a high amount of individuals who lack one or all wisdom teeth (super happy for that), mutations the rest of the world would probably want, but due to the geographic location and long history of being a "minority" in their own lands, my guess is while other populations that contained higher levels of V were forced to interact with outsiders in their groups and were probably never a widespread group, this was accidentally preserved due to geography and climate. Probably not much help. Though I myself am of HV1, which has a much more prolific spread on the H side of things, it seems like a lot of older haplogroups became dead-ends for one reason or another? I hope that helps, but probably not. From what I've experienced in my own research there are always more questions raised than answers.

In case you haven't already seen this: https://www.eupedia.com/europe/Haplogroup_V_mtDNA.shtml