partly because they were telegraph wires and not power wires. most signal cables now are shielded. the voltages that would be induced would likely not fuse most electrical distribution wiring, that's not the vulnerability, it's the transformers, like nostr:npub19ma2w9dmk3kat0nt0k5dwuqzvmg3va9ezwup0zkakhpwv0vcwvcsg8axkl says, they are not radio-shielded, enough, at least. and i think even if that hole was patched, there is a threshold beyond which most of the last mile wires are too thin to cope with the temporary spike in current from the x-ray driven ionization combined with strong/fast solar wind and good coupling between the solar wind polarity and the earth's magnetic pole.