Ukraine spent 18 months planning Operation Spiderweb, where they smuggled cargo trucks with hidden drones on the Eastern side of Russia. Once the trucks launched the drone, they self-destructed.
The key right now is how many of their radar A-50s have been destroyed. They had 8. 2 were destroyed by HIMARS. Now that some of the 6 left over have been destroyed, it will create gaps in their air radar cover.
Russia at this point doesn't have the capability of building A-50s.
There are videos of the losses.