There's no single answer to this question - it really depends on what kind of entrepreneur you want to be and what kind of business you're looking to start. For example certain industries would require some expert domain knowledge.
That said, there are certain qualities and skills that all entrepreneurs have which makes them successful. To be a successful Entrepreneur, you don't necessarily need to be the smartest person in the room - but you do need to be intuitive, resourceful, humble, hungry, competitive, and accountable for your own success.
Therefore it all depends on how we define the word smart. To me smart simply means intuitive, and it is not limited to what I have learned in school. In fact, great entrepreneurs are innovators who change they way things are done or simply fill a gap where there is a need. They ask questions like why and how because they understand that there is not a singular right answer. While most straight A students are not great entrepreneurs because they do not do well in an environments where there not an absolute right answer.
Successful entrepreneurs share the following traits:
- Visionary – “being imaginative, creative, inventive, ingenious, enterprising, and innovative”
- Passionate – “showing or caused by strong feelings or a strong belief”
- Problem Solver – “someone who leans into problems, obsesses about them, and genuinely gets a high from solving them”
- Driven – “relentlessly compelled by the need to accomplish a goal; very hard-working and ambitious”
- Risk-taker – “someone willing to take a leap and willing to fail”
- Responsible – “ability to act independently and make decisions without authorization”
I would highly recommend Gino Wickman's book, "The Entrepreneurial Leap" if you are considering going into business. There are plenty of people with great ideas, who are passionate, but lack the characteristics necessary to execute. The simple truth is most people are not wired to be Entrepreneurs because when it is all said and done, if the idea fails, you have no one else to blame other than your self and that is simply too risky for them.