A group of 5 to 10 guys trained for stuff like this can make life difficult.

Same as with the sea drones. The goal is not to occupy or take territory. It is to deny the enemy their territory and make keeping all of their territory as costly as possible. You hit them in alternating locations and force them to commit resources everywhere, spreading them thin and opening up other weak spots. Guerrilla warfare 101.

But Mali and Syria in the span of a week means the Ukranians have multiple teams making Russian life even more difficult.