Ohanians "great big secret" is that:

It is that we should put forward a serious cause in a fun way.

Explanation:

Ohanian is the founder of Reddit and a successful Internet-based entrepreneur. He is based in Florida and married to Serena Williams. And he has shared his big secret, and which is no matter how serious a cause might be, your effort should be to present it in a fun way. He follows this secret and has made $70M through it. And all will support him on this, like stress, and a complicated tensed approach can make you ill, and you will never live to re-reading such writing in future, and hence it will be a wastage of time certainly. Some will say we should go by the requirement, but I feel Ohanian is right as fun makes our path to find the solution easy, and in any way, there is a risk of not finding a solution. However, always remember some people die with a smile, and they are always remembered as the world loves such personality since they bring to limelight only happiness.