In his post, he wrote about the correlation between the founder's accent and the low success ratio of startups. He found that the stronger the founder's accent is, the harder other people will understand what he tries to say and therefore his startup will be more difficult to succeed.
The founder is always selling to customers, partners, investors and even his employees. The founder's work is to encounter as many people as possible and persuade them to buy his products or ideas. When people meet him the first time, they just think him as normal person they meet everyday. They aren't going to understand him, unless he uses an understandable English. Therefore the founder must be the person who can communicate well in English.