This is a serious development, but reports of the entire Middle East being on the verge of all out war fail to fully appreciate the motives and intentions of the various players.
Looked at from the Israeli point of view, it is an excellent moment to act against Iran in Syria because it is unlikely that the Iranians will respond in a serious way.
In the wake of Donald Trump's withdrawal of the US from the Iran nuclear deal, the Iranians want to show the rest of the world, and particularly the Europeans, that they are the reliable and pacific upholders of the 2015 treaty.
This phase may not last long and does not mean that the Iranians have any faith in the EU states keeping the accord alive. But they do want to ensure that the EU and others will only grudgingly cooperate with the reimposition of draconian sanctions by the US.