EW is unlikely to be placed at these substations. They are needed at the front enough as it is. But then Putin has a whole pantsir are defence unit protecting his datsja.

I'd guess high voltage combined with the range from reciever.

I would guess the distance combined with the low altitude.

one more potential source of interference is from the drone. analog fpv video systems are pretty sensitive to interference from the motors on the drone, and while it seems like the bad interference as in the footage would be fixed quickly, it is a common problem for hobbyists with analog fpv systems, so worth thinking about.