I've read a couple articles on this, since. Probably a bad move on Putin's part (because there was no chance this wasn't an assassination).
Mostly because, when you kill a journalist - or an activist - people shudder, but move on.
When you kill one of top guys, however, it's near the end - you face what Hitler faced. Top brass wondering - am I next? Should I tell him the truth - or lie to save my skin?
I'd be happy about this except that anyone who succeeds Putin will certainly be as bad - the only upside to his removal, is it gives his successor a way to save face and end the war.