We are now beginning to enter the stage of the war where Russia is unable to sustain a general offensive all the way up and down the frontline and must resort to terrorism to project fear and the illusion of unstoppable, corrupted power.
Expect more and more of this crap as Russia is less and less able to credibly fight a ground war.
Remember, acts of terrorism definitionally rely on propaganda creating mass panic for their power as if the perpetrators of the terrorism possessed true power they would have resorted to actual coordinated military action such as fighting on the frontline or taking territory.
In otherwords if Russia chooses to attempt something like this, it is by definition a sign of extreme weakness on their part as was the lazy attempt to claim Ukraine tried to assassinate Putin.
A result of a loss of manpower and eventual loss of political will to continue the war. The parts that Russia controls aren’t coming back to ukraine except maybe the last 30km where russia hasn’t set up proper defences.