According to their blog post, they were left “no other option than to take [their] platform offline” after a court ruling from August. “The judge ruled that Mininova is not directly responsible for any copyright infringements, but ordered it to remove all torrents linking to copyrighted material within three months, or face a penalty of up to 5 million euros.”
It’ll be interesting to see what effect the change to Magnet links has on future court rulings. With Magnet links there is no torrent file, it’s not even a link to anything. It’s just a hash value that the torrent client uses to find the torrent in its peer-to-peer network.