took a quick look, aren't those backlinks to subdomains? No idea what the product/service does but it appears subdomains are the main spam links, not the root.. So perhaps they were duped by spammers creating subdomains
It is a create your own store product. People would have simply been making a store and then using software to spam their links everywhere. I think sub domains are usually treated as separate domains though?
If all the subdomains had links back to zilo (say the header or footer), it starts to look like a huge link farm, or a bunch of satellite sites. It's actually pretty dangerous. But disavow is here, right? hah