So how was this attack gonna generate "revenue" for the attacker? What kind of info did they get hold of?
Often they generate thousands of non-existent pages which get indexed by search engines and just redirect people to Aliexpress pages or other affiliate link sites.
They're adding backlinks to other sites. They're either making revenue from those sites, or (more likely) selling backlinks to unsavory products.
They inject backlinks, SEO spam to advertise payday loans, online pharmacy, casino and so on. Just imagine you can get 30k of links to your website at once. Google will rank that page very high.
One pharmacy shop that sells generics or unlicensed casino can make tens of thousands of dollars per day. So even one week is enough to make a lot of money.