I liked this summation from reddit best. Spoilers below.

"The answer, I believe, is that we are seeing in the movie - at minimum - is the third timeline.

Timeline 1: There is no wormhole near Saturn. Humanity suffers the blight. There are very few survivors, possibly the only survivors use the last of Earth's resources to build a colony in space - possibly they seal themselves underground like was alluded in the film. Maybe humans die off completely and the work of science is taken up by robots who have one, multi-millenia long mission - open a wormhole between our Earth and a habitable world for humanity. After tremendous suffering and thousands of years of effort, this is finally achieve, leading to:

Timeline 2: The wormhole appears near Saturn, and the events of the movie play out like they do in the film. With a couple of exceptions. Cooper is a skilled NASA pilot and he goes on the initial 1st wave exploration missions. Brand follow's her heart (this makes me think there were prior manipulations here to make sure she was on the team, and we're well past the 2nd timeline, but for the sake of clarity lets say that it's a coincidence) and they go to the right planet, Edmund's planet. They set up Plan B. They go home or don't and Earth humanity dies from blight, or at the very least they are very nearly wiped out like in Timeline 1. Tremendous suffering and thousands of years of progress are lost. Eventually humanity evolves to the point where they can manipulate the 5th dimension. In an effort to leapfrog their society ahead by thousands of years of development and progress and increase biodiversity, they develop a plan to save Earth's people and impart them with 4th dimensional knowledge. That brings us to

Timeline 3: They knock Cooper's plane out of the sky and he never goes on the first wave missions. They set him up to find NASA and the events of the film play out. They drop him in the tesseact and allow him set up the chicken-egg cycle that ensures he finds NASA in the first place, and also enables him to send the data to his daughter that she needs to save humanity.

The future beings interfere in these oblique ways because of causality, the wormhole is by Saturn because it's far enough away that it won't substantially change the course of events that eventually allowed humanity (or their robot leftovers) to create the wormhole in the first place. They use Cooper to solve Plan A because it doesn't interfere with Brand's implementation of Plan B. Anything they try has to be out of the way - to not erase the chain of events that led to the creation of the first wormhole in the first place."