It's grimly fascinating to me that people living on an island would find their own conditions so wretched that they would collectively voluntarily abandon the life they knew for one they didn't. It must have been miserable.
I have the questions in the title, but also am curious about the government's position. How did they view the St. Kildans before the evacuation--as a burden or merely as citizens like they would view any other citizens? Did they entice them to evacuate or provide for them in any way afterwards?
I also read that some families would return to visit. Do we know anything about the nature of these returns? How long they were, what they did there, etc. Like, did these families view it as a poignant visit of a time gone by, or did they spend some extended time living there engaging in economic activity?
It's important to remember that by the time St. Kilda was abandoned, it was home to only 36 people, 13 of them children. During the preceding centuries the population of the island had fluctuated between about 100 and 180. Life on St. Kilda became untenable because the community was so underpopulated. The arrival of the cash economy played a role - the islanders had once paid their rent mostly in feathers and lived largely on a diet of seabirds harvested from the cliffs - and during WWI a naval vessel provided regular mail service and imported foodstuffs. This service was withdrawn after the war. Many young people left to look for work on the mainland.
The government did support the islanders in their resettlement, providing transportation for the people and their 1500 sheep. These sheep were sold and the proceeds used to offset the cost of resettlement. The government assisted the resettled folk with housing and jobs for able adult men in the forestry service, where they could put their excellent climbing skills to use. However, there were no trees in St. Kilda, and the men had never had bosses before, so there was something of a learning curve.
Many of the islanders felt isolated without their former neighbours around them. They also complained to the government that the living conditions were not what they had been led to expect. A John Gillies wrote that "this home is worse than the cattle byre I had in St. Kilda."