Sultan Erdogan certainly perfected how to manipulate all the great powers to his benefit by trying to hoodwink both his allies and Russia, Syria and Iran. I think the stupid administration in US led by the End of time Pompeo thought they can manipulate him so as and his irrationality, in the same way they have done with their other ally south so as to be able to benefit from his mad acts and also distance themselves when things go wrong.
I am not sure whether this S-400 thing was co-ordinated with Washington so that a NATO ally can then get insider information about Russia’s defence system but for me the whole episode is bizarre and now there is talk of Turkey acquiring the Patriot missile system.
But maybe Erdogan has run out of luck and also at the same time as we have all run out of luck and economies destroyed by a virus. If Russia and China come out of this better organised than Trump led US then things may change and the US tyrannical rule end.