Long story, short: 1. Realize the world is moving beyond Windows 2. Cede mobile OS to Android/iOS, that battle is lost. 3. Realize, next great revenue stream is the Cloud (Azure).
The problem is they are no longer best-of-breed for any of their markets, except maybe Office. Microsoft doesn't break out Azure revenue, but by all accounts it's quite small compared to AWS. And Office is very much under threat. If you work with young people you'll notice they tend to prefer G Suite apps over Office - most likely because Google has done a great job getting their software into schools.
Not really. But an awful lot of shops rely on their Excel macros. Changing the office suit would mean to re-develop a huge amount of infrastructure.