1. I will first start by saying that I have read, both intentionally and unintentionally, lots and lots of opinions about this.
~ “Russia doesn’t defend Syrian troops against Israeli airstrikes”;
~ “Putin doesn’t verbally threaten Bibi with retaliation should he strike again”;
~“Russia doesn’t give Syria the S1/2/3/4/500”;
Q) Does Israel violate Syrian airspace?
Q) Has Israel directly killed Russian troops?
Q) Does Israel put Hmeymim in any direct danger?
These answers are important. Why?
Israel has not, to date, directly killed any Russian troops. What happened on 17.09.18 was indirect, and there is a very big difference. And I am sure that Tel Aviv knows that this line must not be crossed whatsoever.
Israel hasn’t yet, to date, caused any damage to Hmeymim or put the lives of the soldiers stationed there (on the ground) at risk. The incident on 17.09.2018 came very close to this, but it, all the same, did not cross this line.
I won’t discuss the details of what happened on 17.09.18. Why? Because I consider it to be irrelevant. What is important is how the parties reacted to the incident. And it is here that things become interesting.
Let me explain what it means when inserted into the modern context. The S-400 in Hmeymim represents the Russian state. It represents Russia's foreign policy.
Russia knew that sooner or later Israel would make a mistake. And in order for the mistake to arrive, Russia needed to show patience.
The answer can be found in tweet #38 of this thread. Without the Minsk Agreements, Russia's actions in Syria simply couldn't be possible.