Turning everything off when the panels are at peak output? That lets frequency sag enough that plants start tripping offline to protect themselves and the grid and it'll cascade across the continent in just a few minutes. Then you have a black start which might take months.
There's an excellent video on how catastrophic a black start is. https://youtu.be/uOSnQM1Zu4w?si=x0dA7X7-19CJm6Kf