Dude has been making the same thing for 4 years, he might want something new. If he's got friends in 11bit, no doubt switching completely of product type and working with a smaller team of people you used to work with before could prove refreshing.
Like the founder of Rovio Stockholm is actually a veteran from EA/DICE/Avalanche.
I hope it's for random reasons, that CDProject has a sustainable business culture that allows anyone to become talented and grow, and not that management has gone to shit.
I imagine career growth could be hard in a company with so few games to lead.