The Call of Chulthu is to offer a gameplay totally opposed to D&D and dungeons crawlers, more focused into investigation and survival horror, when D&D PCs are practically one-man-army, even the glass-canon spellcasters.
If I was Hasbro I would worry about Paizo, Paradox Entertaiment or Chaosium being acquired by some cinema or videogame studio, because then those franchises could become true rivals.
There is not only one factor but a combo. CR helped a lot, but also Stranger Things, for example, or those arcades by Capcom, or the videogames Baldur's Gate and Newerwinter Nights.
And other advantage is D&D is the game parents want to play with their children and these are willing to play with the older members of the family. Even Ravenloft or Dark Sun can be not-too-mature for teen players. It is a serious advantage when players can start before when other titles are for +18 (and not only for the threads, but too complicated rules).
* D&D is not only a system and a franchise, but a "metaverse", and only World of Darkness by White Wolf has grown enough to be a potential rival.
And games based in famous franchises could sell more, but these have got a "time limit", and after the licencing deal it was to start from zero again.
* The weak point of D&D is not ready yet to be totally multi-genre and right power balance with the firearms and high-tech. A d20 Modern 2.0. is totally possible, and a new Star Wars d20 but these can't be compatible with D&D because barbarians, monks, paladins and focused melee-fight classes are replaced by gunslingers and one-man-army.
* The 80's cartoon helped to promote the franchise out of the English-speaker countries. I started with the Endless Quest game-books, a loved memory from my childhood. I started to know really the RPGs near of the end of 92 year, thanks by a one-shot magazine.
