Not sure if it's what he meant, but when he says popularity, it's probably popularity among reviewers and journalists. Which is unfortunately real.
There is a big genre/setting bias when it comes to GOTY contenders. Hell, even individual game reviews you can see it. I've given up caring about reviews and GOTY awards.
And it's not necessarily malicious at all. Remember: Who are the people who are working at MEDIA OUTLETS in 2021? Generally, they are somewhat older (30s-40s), especially the people who have any influence on the balloting particularly in big companies (and small indie companies tend to not get successful enough to get a ballot). Those people tend to be people who grew up playing certain games in specific regions of the world. Thus, they also tend to be of similar demographics. I don't know if the TGAs poll media outlets from Japan and give them equal weight, for example. I wonder how many media outlets polled are primarily minority or women led, or are writing for a similar audience.
Generally, the people who don't fit this mold (oddly, probably similar to the WEIRD group that plagues medical science - Western, Educated, Industrialized, Rich, and Democratic - and middle-aged, in this case) but are in games have probably ended up in mediums that haven't had so many institutional barriers (education, money, etc) gatekeeping their way - like YouTube, for example. And yet, the TGAs are not putting YouTubers on the same footing as the games media (though, in another way, they're also embracing influencer culture, so it's a mixed bag).
Due to no fault of anyone in particular (well, let's not get into about systemic institutional bias in media hiring..), you can see how the people who self-select to be in games media may also tend to have somewhat similar tastes and interests on a very broad scale. That's not to say there's no diversity, but simply that what these people say will sound very familiar to other people in this profession. And when they're listening to each other all day, it's not hard to see how "biases" and "trends" can develop within their bubble and then get reported on as objective global fact.
A big ramble lol. But, this is what I think about "media bias". It's 100% real, but it's not necessarily malicious - and it may not be worth trying to combat. Rather, we should be actively expanding the range and diversity of the media sources we listen to if we want to break the biases that exist in the industry. We're doing a REALLY SLOW and generally bad job of that so far. [But, one of the reasons I appreciate that this site has a limited global reach - though we certainly have our own deep, deep myopias here too.]
Anyway, in relation to GOTY, you can see how the possible space of nominations is constrained by so many invisible and subconscious factors. It's hard to get mad at anyone for being so influenced.