GitHub is owned by Microsoft, who is a member of the RIAA who created this legal action.
For Microsoft to pay for the lawyers to take it down (via their RIAA membership payments) and also pay for the lawyers to keep it up seems... rather silly.
From the outside in, there are a lot of aspects of the legal system that look like this - welfare for lawyers. Unfortunately, fixing it requires changing the law and we've made of practice of sending a lot of lawyers to Capitol Hill who are very sympathetic to the needs of lawyers. It's probably the biggest self-perpetuating interest group there is.
