True, there is no evidence of russians being involved. But common sence suggests that such a messy job could not be done in accordance with some mad masterminds plan. Could you imagine the paperwork behind such a decision? No one issues orders to kill civilians unless 100% necessary, because everyone is afraid to lose his job. Most definitely this mission went wrong. The question is who failed? I think it was someone from russian government just because they tend to fail a lot. But I am not saying that someone did not help them fail. One can bribe a president in Russia. Why not bribe a GRU-hitman? Or fool him?
Just speculating here.