The last minute actions against Russia can be viewed minimally as an effort to guarantee continuity of US foreign policy and maximally as a setting up a President Trump.
Obama knows that Trump can simply undo what he has done unilaterally as soon as he takes over. So the question is why is Obama doing this.
Obama is presenting his successor with a dilemma. President Trump either maintains the Obama anti-Russian policy, in which case the effort was successful. Or he doesn't and his presidency is torpedoed if he negates it, making him look soft on Russia or even giving credence to the claim that Trump is a "Russian stooge" planted by Putin, who controls him. This would undercut DJT, possibly to the point of impeachment by a Democratic congress people united in their hate fro him and GOP NeverTrumpers that would prefer Mike Pence as POTUS so they can get on with business as usual. without having to deal with outsiders.
Is President Obama preparing a poison chalice for both Presidents Trump and Putin, and by extension also President Assad, under the guise of being tough on Putin's Russia for alleged "crimes."
One need not be a cynic or a conspiracy theorist to view it that way. Politics ain't beanbag, as they say, and after all, the stakes are world domination.
Watch the narrative on this in the New York Times and the Washington Post. Oh wait, I don't touch either of them even with rubber gloves. But their narrative is reported elsewhere, and I'll link to that.
Trump may lift anti-Russian sanctions - White House official