You are right... that makes more sense in its stupidity - maybe some Cold War leftover that just hates the Russians beyond all measure and reason

Nothing to do with Russia. Assad is an ally of Iran, and rather than having a politically stable and militarily capable nation in that area of influence, Israel and Saudi Arabia (among others) would rather have a chaos-ridden post war Iraq or Libya. But they prefer to have the dirty job done by the US- usually it doesn't take much, a bit of lobbying and tons of newspaper articles about the cruel dictator usually do the trick.