In the grand scheme of it, I haven't worked with that many, but every founder I have had the chance to work with has cared about sustainability. This is way more speculative, but I believe that sustainability goes out the window in favor of quarterly wins when the (co)founder steps back from their role and they transition to a non-(co)founder CEO and such.

I guess we could interpret that as the cofounder cares about sustainability for as long as it takes to hand off the bag.