But if they are ousting their CEO publicly it's probably because things are going extremely badly. I don't think ousting the founder is necessarily making it worse and thus the cause for those companies to worsen after the ousting.

Look up "Rich or King". Companies tend to do better when the founders give away control to people better suited to do the job they would otherwise do.

It just doesn't tend to be very public when it happens successfully.

Paypal? Well, things are complicated.