” ... how does one explain that the Russian S-400 Triumf air-defense system did not work as they warned the USA it would?”
I don’t think the S-400 was used against the US missile attack in Syria. And, at $200m per system, I don’t blame the Russians for not exposing that system to our countermeasures.
RE: And, at $200m per system, I don’t blame the Russians for not exposing that system to our countermeasures.
Well, all those warnings by the Russkies that they will shoot down any missiles fired on Syria are baloney then.
See here for one:
https://nypost.com/2018/04/11/russia-warns-any-us-missiles-fired-at-syria-will-be-shot-down/