Shits old, and the temperature swings probably mean a different load on the grid as people run other appliances. Also with multiple it was probably a chain reaction to some extent.

I don't think they have any way to monitor transformers remotely, which I guess could be the way to be preventative vs. reactive but that costs money and most companies are allergic to spending.

This speculation brought to you by someone who is totally unqualified but taking an educated guess.