I think he's just snowballed in popularity over the years because he's good at reading these scripts in a way that sounds both smart and fun. The different channels focus on different styles and subject areas, letting you pick and choose what kind of thing you're interested in.

I rather like his "Decoding the Unknown" channel, where he gets scripts debunking various paranormal or otherwise mysterious events and he reads them for the first time as it's being recorded, taking lots of opportunities to interject his own theories and speculation and just generally rag on the concept of the paranormal as he goes.

I'm pretty sure he maintains the YT channels themselves, but he has a host of writers who write his scripts

The two Channels / Podcasts I follow are Decoding the Unknown (deep dives into unsolved mysteries and paranormal debunks) and the Casual Criminalist (true crime)

For both, he does a cold read, and often interjects with his own stories and theories