did Russia let it happen?

From my readings, Russians had some inkling of what was brewing in Idlib. It was ignored by the RF general in Syria probably thinking all is good because of Astana agreement with Turkey. Also noting that apparently RF general had been given intelligence reports warning him about the build-up of head-choppers there ... sorry, the moderate rebels : )). Anyways, the current RF general was booted out and the new RF general is now in charge fwiw.

There are alarmist reports saying that RF is to abandon the port in Tartus which I find evidence-free i.e. Russians being out of Syria and abandoning their Med presence. I am inclined to think that it will become clear after the push-back from Russians, Iranians and the Iraqis within (say) 2 weeks. Not sure about Hezbollah, which, at the end of the day, is directly affected in cutting of their supply lines through Syria from Iran. Possibly.