From what I have seen in this conflict, there are a couple of reasons why these FPV drones are effective.These munitions are changing the nature of combat. We saw loitering munitions used by Azeri forces devastate the Karabakh separatists, and their Armenian allies. It was then widely predicted that in a larger war they would be too expensive and too few. Initially this proved correct. Russian forces trying to advance into Kiev used loitering munitions, a few of them. But they were far too few to make a real difference. However as the conflict has dragged on they have become far more widespread. FPV drones, the baby brother of the loitering munition has rapidly outpaced the loitering munition on the battlefield, due to being cheaper. While they have drastically less range and are vulnerable to EW, they are still very cheap and effective when they land. The question of their future remains open, but things like this are likely to be part of it;
While vulnerable to EW, the anti-drone EW systems today are mostly directional. If you can't spot the drone fast enough either via electro-optics or battlefield radar, you can't really direct your jammer to the drone's incoming path/direction.
In any case, both sides seems to be operating in small units. Most the strikes are against standalone or isolated vehicles, where they are operating without the protection of any EW systems. Given the fluid nature of the battlespace, some of these strikes are conducted by teams behind the supposed lines and thus catching their targets unaware.