Giving up the chemical weapons stocks was a master stroke by Russian/Syrian leadership.

1, it kept America out of the civil war (Obama's failed ultimatum, making him look ineffectual and weak[in all honesty, you don't even give ultimatums in the school yard, let alone in world politics!!])

2, freed up enormous resources the syrians had to expend to maintain, and more importantly, safe guard. Last thing the Assad's wanted was rebels getting their hands on large stocks of biological weapons.

3, allowed the Syrian army to mobilise large amounts of troops otherwise tied down ensuring the safety of these sights and surrounds. He whom defends everything defends nothing. 

Form a Syrian point of view, Israel isn't attacking any time soon, better to give them up now, put 100% war effort into overcoming the insurgency, once its quelled, within 12 months Syria can have her Chem/Bio stocks back up to pre war levels. Just in case those pesky jews try and pull something.