I'm intrigued by this. Not sure why you're being downvoted.

This is just speculation, but from what limited knowledge I have about Alaska, even though it is not densely populated overall people tend to live in villages somewhat close to each other, correct? Even if a town only has a couple hundred people, if they all live relatively nearby to one another in a village, buried lines would make sense.

Another possible reason, response to downed lines is probably much more expensive and time consuming in such a large and remote area, so the larger upfront cost to bury lines may pay off quicker than in a smaller state like NH.

Are most long-distance transmission lines buried up there? Or just the distribution infrastructure that goes from building to building?