I can be a blowhard, I know, but I've got real world experience in streaming, strategizing to grab viewers, distributing content, not as a producer or in front of the camera person, but a vampire strategizer sucking the monies from it, talent contract side too. More and more we say the numbers, people under college age primarily watch youtube if they aren't playing interactive video games themselves. They barely watch broadcast tv and watch a tiny bit more streaming.
Youtube: Land of the mmm, pre college crowd let's say. A place where young people have the time to watch stuff and where they go, in fact it scares the living daylights out of MLB, NBA, NHL, the NFL is a little scared but is going to count on gambling to expand and maintain revenue (watch Jerry Jones shove gambling to nationwide heights along with draftkings and fanduel) and the NFL is the 800 pound gorilla when it comes to sports viewership. Most other live sports though, are declining in viewership every year.
So, tennis, tennis kids, do they want to watch this stuff? Tennis adults, wouldn't you think by now these channels have discovered the very limited amount of adults who watch youtube often AND play tennis, AND will watch every video religiously? Probably.
An acquaintance of mine is a successful pokemon card tuber:
https://www.youtube.com/c/Leonhart54/videos
His subject matter, perfect for youtube viewers, his competition from broadcast tv and streaming, none. (as in tennis fans can watch Nadal on tv and not youtube).
Leonhart makes a decent living doing the cards and grinds his butt off to churn content out.
I would say Leonhart is a great example of making a living doing just youtubing, not enjoying great riches, but mortgage paying, feeding, etc. Hard to say any tennis content is reaching this level, yet.
Top of the charts youtuber, the kind that has done national commercials, promoted by youtube themselves, been interviewed by youtube CEO etc. etc.
https://www.youtube.com/c/emmachamberlain/videos
Look at the views, the kinds of shows. It's geared toward, well, I would say 10-21 year olds.
I'm pleased with the amount of people trying tennis videos and putting out good content, but tennis isn't the #1 topic you would choose when designing a profitable youtube channel, even if you started the very first tennis youtube channel.