For me I really do enjoy watching some of the Locking picking lawyers content and he is an expert when it comes to picking locks!
Another few are mental outlaw (although I think everyone knows of him here) and Steven Bridges who makes videos on card counting at casinos and he shows how much he wins/loses from playing
I think “niche” doesn’t necessarily mean “unpopular”, it’s rather about the topics being covered. Without his awesome charisma and jokes he wouldn’t be as popular.