Why? Just because it’s onerous doesn’t mean you don’t have a duty to do it.
If the guy had copy and pasted the whole news article and republished it himself, I doubt many people would try to argue that he hadn’t infringed the copyright of the newspaper. So that thought experiment covers the idea that something can be published legally without automatically granting a licence to reproduce the content.
The question here hinges on whether using opengraph tags on an article implicitly sublicenses the image for reproduction. There’s a solid argument that it does, but the author chose not to test that so we don’t know.
If the answer is yes, then it’s the newspaper who are liable for the infringement by sublicensing the image in a way that’s not compatible with their original licence (I assume! At this stage, we don’t know if the newspaper DID actually have the right to relicense the image for reproduction or not).
If the answer is no, then the author has well-meaningly but incorrectly used the image that the newspaper published. Normally this would probably not be heavily punished by the courts, but the author opted to instead pay the fee, which seems a reasonable approach to take given his uncertainty about the legal grounds by which the image was licensed for use (again, I assume. I doubt it, but it is theoretically possible that X/Twitter were in some kind of relationship with the newspaper that made their usage lawful).
Either way, I imagine neither party I think wanted this to be tested in court. The author clearly didn’t, and the fact that (we are not aware of) the company did not go after X/Twitter despite likely bigger payouts for multiple infringements suggests they also did not, as X/Twitter were more likely to litigate the case.
If the legal system isn’t given an opportunity to weigh in, it can’t do so.
