RE: So many things...
Different teams work on different things. Sometimes they make a quick app in OS version. Those guys get reassigned to another app or to the new OS version. If they can move that original app into the new OS version, it gets done. If not, they will have the original team fix it. Or, they will assign another guy or team to create the app from scratch. Multiply this by thousands of coders. Then add a new innovation that turns the organization in another direction or multiple directions. Imagine trying to be in charge of any organization that size. Sometimes you have to leave things for later to get the product out. Sometimes you have to dump something altogether. And always know that you can NEVER make EVERYONE happy at the same time.