The video player bit seems fairly straightforward if you imagine a monetization strategy involving video ads (which tend to have higher CPMs).
Likewise, the "1 comment displayed" thing seems like a "please consume the media and move on" effort potentially. Remember, they don't make money from you reading comments. They make money from you going back to other surfaces where ads are displayed. Namely your feed or another post.
They're already breaking old.reddit.com. The image gallery viewing UI is hilariously bad on old, and recently I've had a lot of post links having the wrong href (usually to the page you're on or the same as the Next link at the bottom of the screen).
Oddly enough, the video player on old still works way better than the one on new.
Reddit doesn’t want you to lurk without an account or browse on mobile on a browser. They make less money that way. Eventually I am sure they will break old.reddit.com once they think they no longer need the holdouts (who I suspect are a lot of power users).
As someone who has used Reddit for probably 10 years at this point, it makes me sad that some place that I at times legitimately felt like a “member of a community” would break my use case like this (I have accounts but on mobile I sometimes just want to lurk/browse without logging in). But it’s their website and they can do what they want with it. Our only recourse is to complain and try alternatives.