Gary Marcus is a terrific self-promoter and grifter, and there are very large audiences for that sort of stuff. It's simple.
He does more than dunks though, I don't think that's really fair to him. He's trying to position himself as a public intellectual and expert.
I did a quick Algolia search https://hn.algolia.com/?dateRange=all&page=0&prefix=true&que...
If I'm being honest, the combination of the HN audience and him is that he's just a dunk machine. It's all right. I get it. People here like this kind of content. I have to killfile the domain and users who post positively about it if I want to improve my personal feed. That's on me to curate rather than to post Yet Another Complaint Comment (the lesser known yacc).