I think it's just an opportunistic person who saw an easy way to rank their own stuff by taking advantage of your hard work
Like you said -- they ranked higher in some cases (without doing any work besides copying you).
Only the domains that display the stolen content, with no ads or anything.
What is in it for them?
It doesn't make much sense to do it other than if you're trying to affect someone else's ranking by causing them to be penalized for duplicate content. No?
view-source:https://[redacted].com/titansgrave--the-ashes-of-valkana/sea...
unless you have a competitor you really hates you for some personal vendetta, it's exceptionally rare to see this level of effort for the purpose of negative SEO in 2021.
like I said just looks like a spammer going for low hanging fruit, throwing everything at the wall and seeing what sticks
The AD code there is mine and the only thing they added is some JavaScript code for a Russian web page counter ...
Can you please remove the link to the offending site as not to give them any link juice?
I'm not sure that is a correct assessment, just (hopefully) clarifying the OP's intent.