Without having the PivotDesk side of the story, I can't help but feel that there's a second, undocumented failure here: the lack of a strong feedback culture.
Did the cofounder really not receive any performance feedback until "It might be time for you to go"? Did his team members not feel comfortable talking to him about it, or perhaps even the other cofounders, until the situation reached a boiling point? Did other team members know they had an open communication channel to provide feedback about a cofounder?
Unless the issues he describes are intrinsic personality quirks -- in which case he probably needs to understand his tendencies and find an environment where he can thrive -- this whole situation seems avoidable. All employees, but especially managers, should create time and space to have candid, mostly unstructured one-on-one conversations with a handful of direct reports / superiors / peers. Leaders should invite criticism from the very beginning and make sure everyone knows it's safe to challenge ideas and decisions. And ideally, this starts during the hiring process. Let potential employees know that you value productive dissent and do your best to evaluate them on that axis.
If you don't have people within the company that can effectively evaluate you, find someone outside of the company that can provide advice. This seems more common at the (co)founder level, although could apply e.g. to a technical person at a highly non-technical company as well.
EDIT: As a cofounder, he had the power to engineer some of these support structures himself. This isn't "mean company ruins struggling cofounder," but rather a reminder to spend time on soft skills and the human element of running a business.