Part of the interview process is for people to see each other. The reason for this is so that they can judge how they answer questions, deal with surprises, verify good hygiene, know who they interviewed so they know who to expect on the first day, make sure they dressed appropriately, and more.
With the recruiter having their camera off, they did you a disservice, since you can't judge them back. Maybe they were just having a bad hair day, but that doesn't dismiss what they did.
Interviews are a two way street, since you need to be judging them just as they are judging you. You need to verify that they are doing the interview from a professional environment, take reasonable care of themselves, and all the other things I mentioned above. If you aren't comfortable with them and their setting, just like they need to be comfortable with you, you shouldn't take a job.
Unless it's specified beforehand, you should keep your camera on during an interview. This shows you aren't hiding anything. If they don't have their's on, it can be a red flag. A single red flag isn't a deal-breaker, but many red flags can be. If this is the only red flag, still do your research on the company to make sure they really aren't hiding anything. And quickly turning off your camera, or not having your camera on when you should, is a red flag to them.
If you don't get this job, consider it a lesson and move on. Don't berate yourself for it, since there may be other factors you don't know about that didn't match you up to this job. And if this was the only red flag that disqualified you, you're better off not working for a company that's this picky and hypocritical about their employees.
