"What is or isn't art" didn't simply become a topic because people like to philosophize about the meaning of words. Over the 20th century the art world took fascination with the subversive, transgressive, the postmodern, rejecting authority and standards of beauty that were deemed limiting and oppressive etc. One direct contributing component was photography. Skill of realistic depiction became deemphasized, with mass production, plastic etc., the focus became abstract ideas. It was also a protest against the system that brought the two world wars.

It was considered "anti-art" at the time, but basically took over the elite art world itself and the overall movement had huge impact on what is considered art today, on performance art, sculptures, architecture that looks intentionally upsetting etc.

It's not useful to try to think of the sides as "expansive definitionists" who consider pretty much anything art just because, and "restrictive definitionists" who only consider classic masterpieces art. The divide is much more specific and has intellectual foundation and history to it.

The same motivations that led to the expansive definition in the personally transgressive, radical and subversive sense today logically and coherently oppose the pictures and texts generated in huge centralized profit-oriented companies via mechanization. Presumably if AI was more of a distributed hacker-ethos-driven thing that shows the middle finger to Disney copyrightism, they may be pro-AI.