Once the beings that survive to evolve into beings that exist in the 5th dimension move to a place where they exist in the fifth dimension, remember that they don't see time linearly like we do. All time is simultaneously present before them. Being able to see all time simultaneously, they can also see the reactions of their actions.

Imagine time being like a small flowing stream of water. A little study of the stream, of the stream bed, and the water would allow someone to know exactly what sort of manipulations they would need to make to divert the stream down a different path. Place a large enough rock in the right place and you can change the course of the stream whichever direction you want. In that way, the beings that exist in the 5th dimension might have been able to know that simply preventing Cooper from being one of the first out would cause a chain reaction that would lead to Cooper saving the whole of humanity instead of just a part. It is possible that in earlier recursions of the time stream Cooper made it to NASA later, under different circumstances. Cooper interfering with his previous timeline would be like an eddy in a stream that is self-creating and self-perpetuating, but not necessary for the stream to continue to flow in the same direction.