This is a very good article in the IEEE Spectrum.
The U.S. Congress set us on this road in 1982, when it created a centralized appellate court for patent cases called the U.S. Court of Appeals for the Federal Circuit. A decade later, Congress ordered that the U.S. Patent and Trademark Office (PTO), which up until then had been funded by tax revenues, instead fund itself through application and maintenance fees. Both changes were described as administrative and procedural rather than substantive.
But now, after still another decade, it is apparent that together these changes have resulted in the most profound transformation in U.S. patent policy and practice since the Patent Act of 1836. They make it easier to obtain patents, to enforce patents against others, and to extract large financial awards from such enforcement but harder for those accused of infringing patents to challenge the patents' validity.