Conjecture & innuendo based on attributions about an unknowable set of circumstances.
Didn't try hard enough with Maliki? None of us were there to make that assessment, so what we "feel" is merely projection.
The rest of it? The withdrawal timetable is as GWB and the Iraqis agreed upon years ago. I'm confident that changing circumstances could lead to changes of plan, but that seems unlikely. I'm also confident that if the Iraqi govt asked for US help, they'd get it.
The Iraqis want us out entirely, and if they are indeed a sovereign nation, particularly a non-belligerent friendly one, we're obliged to comply with their desires. That option was left open in the original agreement that GWB made, and the Iraqis have chosen to exercise it.