Why did the high-voltage tower break in a bad snowstorm?

In the south, the air humidity is very high. When the temperature is below 0 degrees, rain will fall and freeze into ice immediately after landing, including wires and iron towers-this is different from the north, where it snows and won't freeze in the air-which is freezing rain. The thickness of ice on wires and towers is getting bigger and bigger, reaching 6 ~ 8 cm on average, and the huge gravity becomes a huge pulling force on towers, while the design of towers can only resist ice with a thickness of only 3cm, so it is easy to be pulled down and broken.