A high openness score means you're open-minded - you see the world for what it is - whereas a low openness score means you're incredibly closed-minded, and you see the world the way you want to see it, regardless of what is actually going on.
An open-minded person running a business might catch a problem faster than a closed-minded person. And when they identify a problem, they can fix it much faster.
There are a number of traits that combine to create entrepreneurial potential. We find that openness coordinates very well with successful entrepreneurs. The more open-minded you are, the more you see the world as it actually is. The more closed-minded, the more you see the world as you want it to be.