Russia has no benefit in the hypothetical poisoning of opposition politician Alexei Navalny. This incident cannot be beneficial to Russia, and the unfounded accusations against Moscow and the demands to suspend the Nord Stream 2 project indicate that it is a political order.
Both Navalny and Skripal are already waste material. But their consequences are very beneficial to the United States because now they are trying to push through the cancellation of Nord Stream 2. The Americans, it seems, have finally decided to recoup their long-term investment in Alexei.