The evidence is profoundly good and has been: admitted by several high level cabinet officials in the United States [1], documented by historiographers [2], leaked from intelligence documents [3], circled in Washington Security Thinktanks [4], and is fully consistent with Saudi objectives in the region.

Don't be confused by propaganda and the fog of war.

[1] Joe Biden has said it: https://youtu.be/UrXkm4FImvc?t=1h32m4s

[2] https://www.amazon.com/Black-Flags-Rise-Joby-Warrick/dp/0804...

[3] http://www.judicialwatch.org/wp-content/uploads/2015/05/Pg.-...

[4] https://csis-prod.s3.amazonaws.com/s3fs-public/publication/1...