Every company has their time in the wilderness - MS just emerged from theirs, Apple had theirs, and Google started theirs a while back.
They're usually caused by hubris, and learning humility, to not antagonize your customers, and that you can make mistakes - like Microsoft seems to have - usually fixes things.
Really good point, unfortunately I think one of the biggest reasons any big company does get out of "the woods" is through competition starting to scare them.
Its fairly obvious that google is not really afraid of any large competitor in their space.
More than anything they are just buying up the next google (like msft did) to ensure that nobody can come up from the depths.
Except that it was likely investors pushing Google to come up with a response to Facebook that caused them to create Google Plus, even though in the process they had to kill several more vibrant social networks that had organically grown around their existing products.
Desperate imitation of Apple caused additional problems.
They're usually caused by hubris, and learning humility, to not antagonize your customers, and that you can make mistakes - like Microsoft seems to have - usually fixes things.