There could be a whole host of reasons for this, unfortunately. Sometimes they put candidates on hold, sometimes they rank them on some basis and prioritise inviting people on that ranking. It could just be down to luck - maybe the person allocate your video interview just hasn't reviewed their's yet while other people in different batches have been allocated to other reviewers who have managed to review their work.
As it has only been two weeks since you received the video interview (although it will be more important when you completed it rather than when it was sent), I would generally advise not chasing up so soon. However, on this occasion, it is for a winter scheme that will only be a matter of weeks away, and therefore a brief email asking when you may hear back in regards to a decision on your application would not be seen as unnormal or unexpected. The only time I would advise against this is if you only submitted your video interview answer in the last 5 working days. Then I would wait until next week or so to follow up.