But that Creative Commons licence was issued from the copyright holder of those videos, not the people in them. The people in those videos may not even have agreed to appear in the video if they were in a public place (the relevant legal term, at least here in the UK, is "reasonable expectation of privacy"). So if Kaggle requires people in the videos to consent taking part then that consent cannot be inferred from that licence.

What's more, if that consent is not legally required (there's a heavy "if" in this sentence, IANAL so I do pretend to know whether it's required e.g. under GDPR, but let's assume for a moment that it's not) then Kaggle are still perfectly at rights to ask for that permission to qualify for their competition. After all, it's their competition, and it's totally reasonable for them to set an ethical criteria that's even higher than legally required.