Without moving blame off Russia it's not like our own nation has clean hands when it comes to deaths of innocents caught up in these geo political chess games, one only needs look to Iraq, Libya and Syria and the millions either displaced from their homes or killed as a result of our own meddling in trying to overthrow regimes and destabilise those regions which are often friends with Russia.
And it's not new this has been happening since WW2 from Korea, to Vietnam to Afghanistan (80's and 00's).... the list goes on
One would think that if Russia really wanted him dead, they would have arranged an "accident" for him whilst in jail ? But no, it's better to kill him years later in a foreign country and cause a political **** storm from it all
There's also another option in that it's not Russia who killed him but Mossad, N Korea, BND, CIA, MI6 in order to create political instability because guess what ? The timing is rather convenient considering it's Russia's election period