Just how many millions of people do those outdoors activities?
You can't survive selling solely to YouTubers, that's definitely true, but you don't need to. Just like tennis companies don't need to survive solely on selling to Grand Slam competitors. Plenty of people are willing to spend a few hundred bucks on their hobbies if it gives them nice pictures and videos for InstaSnapBookTok and to show off at parties.
And no, normal cameras and smartphones are not enough. They'll do for a casual hike, but they will not survive being attached to a mountain bike going downhill and being shaken to bits. I found out the hard way, it is how I killed my first smartphone. If you disagree: why not try it out yourself with a $1500 flagship phone and report back how it went?