I find what happened there to be ambiguous and Bethesda likely set it up that way similar to how some writers like to have ambiguous endings. You can accept the simple and boring explanation, but the evidence also points toward a town that destroyed itself due to everyone taking a side in a bloody conflict and the last remaining person leaves, dies, or commits suicide due to the horror that they witnessed. After all, there is no witnesses to tell what actually happened and all that is available is a holotape, terminal entries, and a note to figure out what might happen. Can't go into detail since this is not the Spoilers section.
You can use console commands to create a settlement anywhere provided there is a workbench in the area. I think it is based on cells. For example, spawning a workbench in Vault 111 will allow you to create a settlement in Vault 111 which never made sense why you couldn't make Vault 111 into your character's home. While spawning a workbench in the outside world would have undefined limits that are only noticeable when you receive the leaving workshop area message. What you need to type for console commands is:
tgm
player.placeatme c1aeb (Workshop)
player.placeatme 20593 10 (Spawns 10 Settlers)
Then press v to go into the workshop menu.