Yes, and Yes. It was more common some years ago to bring in professional leaders when either the founders screwed up OR the investors felt that professional leadership could take the company to a new level (I was brought in to fill the CEO role 3x in this scenario). I don’t know the specifics of the founders departure, but it could have been either their choice (i.e. they quit) or they were being too disruptive upon the hiring of the CEO and forced to leave (ie. given a package).
Again, I don’t know the specifics. However, what was likely taking place is twofold: 1) Many
employees were pissed at what a lousy job the new CEO and his team were doing and reached out to the founders, and 2) subsequently the investors (lead: Sequoia Capital) reached out to the founders to give them another chance, this time providing greater guidance (many forms of this). As for the personal grievance, the founders passion for the business likely was greater than holding a 3 year old grudge.