All of the above? Throw in corrupted management that doesn't realize you can't coast on an old reputation forever, and if you keep letting quality slide eventually there will be a watershed moment.

As an aside, I think you can see this happening in California right now. California (and more specifically SF) has been winning for so long that now public officials have drunk their own cool-aid and seem to think Cali/SF is some sort of magic place and it's all the things they've done which have made it tech mecca. Except probably it's not, and that will become obvious as everyone slowly wakes up to that.