Early on in the pandemic, Youtube was demonetizing videos related to COVID-19 as they do for numerous other sensitive topics like war, death, or terrorist attacks. Many Youtubers would therefore be cautious even mentioning it tangentially to prevent that potential demonetization. I think it has been months since Youtube adjusted their policy on this to allow monetization (EDIT: Yep, this policy was changed over 3 months ago[1]).
[1] - https://techcrunch.com/2020/03/11/youtube-will-now-allow-cre...