In the context of entrepreneurship, passion is not about ‘This is my hobby” kind of passion. It is about “I am excited enough about the domain to consider committing my current life in building a business around it. I like doing what is involved in doing the business, around this concept”.
Passion or rather deep interest is important because every business will go through its challenges. If an entrepreneur is not passionate about a particular domain, and its potential to create wealth through a venture in that domain, investors are vary that the person may give up at the first signs of serious challenges.
On the other hand, someone who is committed to a domain because of an underlying passion/interest is more likely to survive the rough times.