For helping to give them a back door exit from Syria.

To the Iranians a message is clear :no the Russians and no Assad are interested in a war with Israel, so take your troops away and forget from a war with Israel.

This is not 550 B.C. Now Israel has the ability to annihilate invaders. No one way destruction of Israel, while enemies reap all the benefits at Israel's cost.

In this case the decision to go on record was election point scoring for Netanyahu as he knows 99% of Israelis will be happy about it so won't cost him any votes but at the same time it was the right thing to do because it sends a message to Assad & Iran that whilst you might have the S-300 and we do not have Russian permission anymore we will not be detered and as long as you shelter Iran we will strike.
Considering that everybody knows who did it anyway and the policy is neither admit or deny anything rather than deny then its no different to going on record and saying we did it.

Cause Syria claims that they shoot down most missiles.. pretending that they are strong ..

just please start doing that in other areas of governance and we'll be happy campers.

this regime has dug itself into a huge hole by making numerous enemies
who hate them.
the regime has almost no allies, not even russia.
all russia wants is to preserve the assad regime so as to allow russia
to maintain its ports and bases in syria. however, russia is not
interested in a war to advance iran's interests.

I think the real reason is that Bibi beleave it will help him on elections.