Tony Vargas
Legend
And the lack of errata (no matter how badly 'needed' it might seem in a technical sense). A stable presentation matters in defining & building a brand. People can fairly quickly find out what D&D is, now, in a way they couldn't have in, really, any prior period. There's no 'two pronged approach' like in the fad years, there's not a zillion settings like in 2e, there's not a ton of supplements like in 3e & 4e. And, of course, there's being able to view streaming examples of play - you could do that with 4e, too, but you'd also find irate grognards condemning the whole thing and videos of book burning, as well.Agreed. The product release pace is a vital element.
In one sense, the success of 5e is amazing.
In another, it's just competent brand management.