Here's a gray market "business model":

- Hacker H hacks site, injects cryptomining script

- Because H doesn't want other hackers to do the same, he will make the site secure and thereby kind of "maintain" it (in a security sense)

- Because H doesn't want the site to slow down endlessly, he will use cryptomining "as much as possible" while still keeping the site sufficiently responsive (otherwise traffic would go down and net income would decrease in the long run)

End result: a kind of a symbiotic relationship between a gray hat hacker and a standard web content provider.