Just to add, I was at a University campus when the entire building's electrics went out and there was a significant pull due to relatively powerful computers in every room. They initially tried to bring the building back online altogether and failed. Then they tried to bring it back in sections and failed too. In the end they ended up going into each lab, turning every computer off at the wall to bring each lab's power back, and then turn each computer on one by one.
I can only imagine the difficulty of bringing large parts of the grid back online, that rush current must be immense.
Yup. I used to work with a factory that had a bunch of really big machines. Turn everything on at once and the transformer out on the pole self-destructed. Note that the breakers didn't pop--the startup transient was short enough. The power company wasn't happy.
Or look at Apollo 13. The astronauts had turned off everything possible because they had lost their generator and only had their batteries. And it took a lot of furious planning by the guys on the ground to come up with a sequence of turning things back on that didn't cause the peak draw to go too high. Can't go too fast or it trips. Can't start too early because the power is limited, but can't start too late because the systems have to be up when they hit the atmosphere.
I can only imagine the difficulty of bringing large parts of the grid back online, that rush current must be immense.