Wait, why are they attacking Syria.
5 of their soldiers got squished to death from an ISIS truck driver and they are attacking Syria. why???
Assad is fighting ISIS for fucks sake.
Geopolitics are very confusing in Middle East , to say the least !
For Israel, the main threat identified after Gulf War One in 1991 is Iran. They see Iran as a potential nuclear rival . Israel is now very close of being KSA best ally in the region because of this shared perception of Iran. So every ally of Iran such as shiite lebanese Hezbollah or Assad's regime can at times become targets.
Isis, on the other hand , is not seen as a serious threat because it has no access to sophisticate weapons .
One could ask : why Israel isn't doing more to help the Syrian rebel forces, whether moderate or radical , in order to weaken furthermore Iran ' s allies ?
Answer is probably that Israel is assuming that this war has no issue and that picking a side could backfire in the future. Let's imagine that Israel starts using Hamas Palestinian sunni fighters as cannon fodder to help the rebels. Let's imagine that these Hamas fighters successfully turn the tide against Assad and eventually help the rebels to win the war ... then Israel may end with a new unpredictible ennemy at its northern border.
Israel is fine with the chaos in Syria. It keeps busy Iran and Hezbollah for a long time to come.