They aren't suing every Android OEM out of necessity. Microsoft has converted to patent troll in lieu of innovating in the mobile space.
There's nothing preventing a sufficiently large company from being some fraction X and another fraction Y.
All systems have bugs, which is why simpler systems are easier to manage in the long run.
If they wanted to crush Samsung, they'd insist that Samsung sell WP7 phones or nothing. If their patents hold up, that is their right.
The term "patent troll" was used as early as 1993 to
describe companies that file aggressive patent lawsuits.