I think patents are usually granted if filed in the correct format. The expectation is, challenges are where weak patents are discovered. The patent office hasn't got enough lawyers to examine every application.

Also, trolls rarely are the ones creating these patents. They just buy up some basket of idle patents, then spend their morning looking for any company announcing anything that has a couple words in common with something in their 'portfolio'. They send a boilerplate royalty request or whatever. Rinse and repeat.