One of the largest challenges in any political dispute with Moscow has been traditionally its overwhelming arrogance and feeling of impunity. This is what allowed them to blatantly deny any involvement in Salisbury, Crimea, MH17, Bucha etc in spite of hard evidence - their unsaid answer was always like “yes, we know we’re lying and we know you know but what are you going to do?” Seems like Ukraine decided they’re going to put a price on this tactics of theirs.
As for the Western reactions, I recently watched a very relevant interview with Yigal Levin[^1] who said, commenting on the Belgorod incursion, that it’s very much in the interest of Ukraine to take the war to the enemy’s territory. He argues, if Ukraine is the only party suffering losses to its people and infrastructure, then of course Russia can continue it for years. He also said this was always very much Israel’s policy in response to much larger hostile countries that surround it, and it was exactly how demilitarisaion of Sinai was achieved after 1982, effectively ensuring long-term peace. Levin also said that in such as huge disproportion between Israel and its enemies, both in terms of human resources and military objectives (Israel - survival, everyone else - eradication of Israel and Jews), Israels’ allies are ready to tolerate - not praise, approve, encourage but specifically tolerate - some tactics they would not approve of in a more balanced armed conflict.
At this point, I still have very fresh memories of the war in Chechnya, which was of course also asymmetrical conflict, but at some point Chechen leadership quite openly approved of indiscriminate violence against Russian civilians (kidnappings, beheadings, bombings etc). I intuitively very much understand there’s a clear boundary between an UAV flying into Kremlin or Rublyovka and Chechen airplane bombing 2000’s style but I must admit the boundary is more vague than a clear “no attacks on Russian soil” policy before.
On the other hand, Russian society and elites don’t seem to be any more unnerved about the war in Ukraine than they were in 2022 and the state propaganda is impermeable, so maybe this is the factor that resulted in change of tactics.