Probably like what happened in the 2003 blackout. A fault occurs in a section of the grid and instead of isolating the area the excess power is sent down the line which causes another fault which sends more power down the line until the entire grid fails.
No, I did that one too. I was in Detroit. First they said it was a substation downriver. Then we realized it involved multiple states. So the power outage was not centered around Metro Airport.
I never did hear exactly what regions were all involved.
We didn’t have power and were trying to get a wedding to go off uninterrupted.