Russia had an absolute massive stockpile of air defense assets at the beginning of the war. Ukraine has steadily worked at degrading these assets over time. The more they destroyed the easier it was to destroy the next asset.

At the same time Ukraine has massively increased it's drone capabilities and numbers at every range. So the remaining Russian air defense has to work harder with less numbers against more drones.

The longer ranges of Ukraines drones also means that Russia has to defend more area with less equipment. Russia is forced to prioritize assets to protect.

Today Moscow has a robust air defense system but whole sections of the front have close to zero. Ukraine has total freedom to hit any target they can find in many regions.

Russia is seeking to figure out a cheap effective way to defend their airspace. At the same time Ukraine is relentlessly damaging the infrastructure Russia needs to build the new anti-air capabilities.

The others mentioned the improved financial situation and development of longer range drones.

The Russian advances have stalled since the start of the year indicating that the war was already close to a turning point. And Ukraine has been hunting down Russian air defenses for well over a year now with success.

Basically, Ukraine now has the technology, the finances to produce the technology, diminished the countermeasures against the technology, while the war reached a point where Russia no longer can reliably resupply their countermeasures. It can only get worse for Russia at this point as long as Ukraine continues to receive sufficient finances and materials.

Hungary is no longer blocking EU money in Ukraine, and it appears Ukraine has switched up it's targeting priorities.