Because the people of America just blinked.
How did we blink on 9/11?
We should all get used to this! Did we really think that Rebublicans would we in charge for the entire course of the War on Islamofacism? Why do you think the Cold War took almost 50 years? Because there was a back and forth of power between the hawks and the doves. This is expected and normal. We should take a breath and realize that this is the early days of a long term war. Attacks by the enemy will ensure that this issue stays mostly in the foreground for a long time to come.