It's human management. A lot of people overlook that as something important in business. They think once they have money, they can run any business they want but it's not 100% true especially when it's not a business you will be managing only by yourself.They often fall to the illusion that they are so good at doing something, they can do it themselves. That hype towards startups, everyone in jumping into that.
The main problem is, you need to handle money and people like a pro when you are doing business. If you fail in even one of this, that's the end of your entreprenuership.