Microsoft Stream will tell you how much of the tenant storage allocation has been consumed by uploaded videos, but not who’s uploading the videos. You can find out by looking for video upload events in the Office 365 audit log. Once found, it’s a matter of processing the events to extract useful information!
The swelling interest in Teams has driven interest in online meetings. The recording generated from Teams meetings end up in Stream, but how much storage is consumed by these recordings? Stream will tell you an overall figure, but you won’t know how much storage is consumed by individual videos or who’s taking up all the space.