From what I understand the cartels have made it impossible for the pirate bay to use legitimate ad networks. And they cannot accept donations easily, only bitcoin which no one who uses the pirate bay to get files would know how to use (it's after-all a bottom of the barrel torrent site). So they've turned to this.
Honestly at this point the site only serves as a shield for other pirate sites. With all the focus that TPB gets it helps take some of the heat off smaller sites that are higher quality. So for that I hope they stay around a very long time being that beacon that attracts all the worlds anti-piracy like moths to a flame.