This isn’t true. In most places I’ve been, electrical lines have all been elevated on poles. Where I currently live, there is a pretty intensive line clearing program each spring to keep the lines clear. Even in places where house level lines were buried, the middle transmission lines were still elevated.

And I believe all high voltage transmission lines are above ground.

The difference is that California historically has fire prone conditions. It’s not like the rest of the country is doing something different and California has done something inherently wrong. It’s that California did what the rest of the country was doing, but without conditions to support it.