Can We Expect Intelligence from the Director of National Intelligence?

I'm still trying to get my head around a glaring issue related to the Benghazi attack. On the subject of who changed the CIA's talking points regarding the attack, how can we not know who did it?

The attack occurred on 9-11-12, right? According to Gen. David Petraeus, the Central Intelligence Agency initially assessed the attack as a terrorist strike carried out by Ansar al-Sharia, a Libyan offshoot of al-Qaeda. But despite that initial assessment, Petraeus, then head of the CIA, told Congress on 9-14 that the attack had started with a protest about a movie. Why did Petraeus say that?

On 9-14, Secretary of State Hillary Clinton blamed the movie in her address at the transfer of remains ceremony. Why did she do that?

On 9-16, Ambassador Susan Rice blamed the attack on a protest when she appeared on five Sunday political shows. Why did she do that? Who changed both Rice's and Petraeus' talking points during the five days from the attack to Rice's star turn?

For about ten days after Rice's five-spot, President Barack Obama continued to blame a movie and dodge the possibility that Benghazi was a terrorist attack.  He blamed the movie six times during his address at the United Nations on 9-26. Why did he do that?

We're told now that someone within the office of Director of National Intelligence James Clapper changed the talking points. We're told that that person was not Clapper himself. The DNI's office is apparently at a loss to determine who did change the talking points.

How is this possible?