what would make all of the interior lights go out at the same time?

A blown fuse, broken wire, corrosion on wire, Switch off on dash. True story...my wife told me all the cluster lights were out in our van. She told me she used her cell phone to light it up during a 20 mile trip home. I went outside and spent 30 minutes checking fuses, relays and continuity in circuits. I found no issues. I then checked the switch on the dash and it was off. Dimmer switch that goes down to off... she laughed for 20 minutes about this. She is not blonde either. I asked her to buy some hair color to change it to blonde. It is our inside joke now when people ask me to diagnose their electrical issues.

Yes definitely check the interior dome/dash lights dimmer wheel or switch. And if thats what it is then grab the blonde hair dye.