Just got back to one of my settlements (Starlight Drive-In) where at first everything is normal
- Water is at 220
- Food is at 108
- Power is at 250
- Defense is at 447
After about 1 minute in the settlement, all the ratings go down. Both my fusion generators just destroyed themselves in front of me. Then, half of my food supply goes with the mutfruit plants destroyed out of nowhere and my water purifiers get destroyed.
No there was no early warning notification saying “defend starlight drive in” or “starlight drive in is under attack”, and no enemies appeared.
I’m wondering if someone could tell me why my settlement decides to randomly destroy itself without an attack even when I’m in said settlement when it happens.
As Nelson mentioned in a comment, you have most likely built too many buildings/crafted items in that settlement. Unless you’re on PC and are running a few mods, settlements have a capped size in which to place buildings/crafts.
Take a look at this question to get some more information on how size is calculated in a settlement. Most likely your buildings/crafts were destroyed in order to lower the settlement size.