If you're taking a fail fast type approach, the business guys fail faster when they can't get a tech co-founder to rally around their ideas. If you can't do that, you probably can't sell the MVP either. On flipside, the tech guys will spend month and even years polishing their 'product' without ever actually launching it with actual attempts to sale it. So they fail slowly after sinking tons of time. They'll talk about it as a side-project to minimize the appearance of failure but if they put all that work in they really do want it to succeed. They just get to the point where code is good enough and can't force themselves to transition to marketing/sales/etc.