It's certainly hard to find one person in a group of players who can be a _good_ GM.
Regardless, I think the key difference here isn't just connecting D&D players, it's more that the GMs are professionals. It's the difference between a professional "murder mystery" dinner, and one that a friend organizes. Sure, the format is largely similar, but the experience is wildly different.
Is it really so hard to find one person in a group of players that wants to GM?
Is it really that hard to find a group of players in the first place?
Meetup has always been perfectly adequate to find a group, and I have to do that only once for every place I live.