The Convoluted Path to ‘Chemical Weapons’ Belief

The path from Monday to today, which has brought the US to believe Syria’s chemical weapons use is unusual. This timeline may help us better get a grip on how (though not why) officials got from A to B.
Monday: Chuck Hagel is in Israel speaking with Israeli Defense Minister Moshe ‘Bogie‘ Ya’alon. According to Hagel, Syrian chemical weapons didn’t come up.
Tuesday: Israeli Brigadier General Itai Brun delivers a speech in Tel Aviv claiming that Syria has “repeatedly” used chemical weapons.
Later Tuesday: Secretary of State John Kerry calls Benjamin Netanyahu to specifically press him on Brun’s claim. Kerry says Netanyahu was unable to confirm the allegation at all, while Netanyahu’s office refuses to make any public comments on the call or Brun’s claim. Kerry follows up with this non-proof by pushing NATO to send more aid to Syria’s rebels.
Wednesday: Hagel points out how weird it is that no one in Israel told him any of this stuff during his visit, in which he (civilian leader of the US military) met with Israeli military officials.
Thursday: The White House says it believes Syria has used chemical weapons on a “small scale.” Hagel says he believes that too.
The holes in the story:
1. Israel’s military claims to have provided the evidence on which Brun makes his statement to the US, even though Hagel has apparently never heard of it.
2. Conversely, Israel’s military suggests that Brun’s assessment is based in large measure on “visual evidence” i.e. photographs from Syria’s rebels of people foaming at the mouth. This “evidence” was certainly familiar to the US before Monday, and they still had repeatedly said over the past weeks that they didn’t believe Syria had actually used chemical weapons.
Other things worth noting:
3. Brun claims Syria used chemical weapons five times. The US “assessment” says twice. Media reports of rebels claiming chemical weapons use are common, but only twice did the reports get major coverage. The more recent of the two saw Syrian troops killed by suffocating gas, leading analysts to believe that the rebels had used a make-shift lachrymatory agent as a weapon, not the “nerve agent” that Syria’s arsenal consists of and is accused of using. The US ended both of the major reports claiming that they didn’t believe chemical weapons were used, but now say they do, based only on “evidence” that they already had and already dismissed.