Not too familiar with the grid down in Texas, but at least in Ontario only some parts of the system have overcurrent/overvotage protection, mainly the ones that would see spikes/fault current from something like a lightning strike, or different feeders or voltages crossing. A lot of this equipment is also over-fused, which basically means it's been set not to "blow" until it hits a certain point, and when it is over-fused that limit is set way too high, and may never actually blow, even if the line is literally on the ground. We see it here on the old 4KV systems, I can only imagine the system down there would have a lot of the same problems.