I will not promote: Why do I want to co-found with a friend instead of doing it alone?

So I'm an American, but I live overseas. I worked for a few years and then got together with three other Americans I met in the country to start an import/export company. It went pretty well, but some things came up and I had to leave the company and go back to America for half a year. Now I'm back in that country again, and since I'm not a co-founder anymore, if I rejoined I'd be an employee. Two out of the three co-founders are pretty upset with me because I left them at a crucial moment, so they've been