Electronic warfare is pretty effective against drones that are using radio waves for their communication. Earlier in the war you could see a lot of drone footage that would become washed out with static as they got closer to tanks so it's much more reliable to use spools of fiber.

The RF communications they use are not robust in so-called denied environments, so it is relatively easy to severe the link with EW even if it is not that sophisticated. The use of fiber is a workaround that gives the drone a reliable control link. It does not protect the drone against direct EW (e.g. attacks against the onboard systems).

Robust RF communication for denied environments is tech that exists, it just doesn’t seem to be present on the Ukraine/Russia battlefield. This is likely because so much of the drone tech is derived from consumer platforms and both sides have limited access to sophisticated military-grade RF silicon.

To counter EW measures and also in challenging radio environment. Like to fly into hangar with stored tanks 20+km from the frontline. Or into the canyon, places with so called radio shadow.

To counter jamming and GPS spoofing. https://spectrum.ieee.org/killer-drones