1 The alleged founder was arrested
The alleged founder, Artem Vaulin, was arrested by the US government inside Poland. This move led to the shutting down of the site.
2 The US seized the domain names
The US authorities seized the domain names associated with the site, thus preventing it from coming online.
3 One of the servers was located in Chicago
The reason the US government was able to charge Artem Vaulin is that one of his site's servers was located in Chicago.
4 Copyright infringements charges
The founder is facing charges of copyright infringement, as the website allowed people to illegally download software and files that are protected by copyright laws.
5 Distributing $1 billion of copyrighted materials
The founder was charged for distributing well over $1 billion of copyrighted materials. (See Why is Groupon failing?)
6 Confusing copyright claim process
The site uses a lengthily and confusing copyright claim process to prevent people from completing the process to the end and so keeping the copyrighted material on the site.
7 It had some of the big copyrighted titles
The site had some of the big copyrighted Hollywood titles, and as a result, it got more attention, which eventually led to the lawsuit. (See Why did Radioshack fail?)