At the very least, we know who those people are. Why not prosecute them?
First you have to investigate them. And if they can’t prove they moved to NH sometime in the past year, you’re right, they should be prosecuted.
Their social media networks should also be investigated to determine which direction they lean politically, if any. I suspect anyone willing to commit voter fraud in such an obvious manner would be sharing their political thinking online.
It should be relatively easy to determine if these individuals voted in their previous state as well as New Hampshire.