My buddy’s parents were huge Lord of the Rings nuts when I was a child and they always said that a movie adaption could not be done. The lore, the scale, the depth... just wasn’t possible.
It was a perfect storm of right place, right time and the presence of Mark Ordesky at New Line Cinema. A rabid tolkien fanatic since his teens, Ordesky was Jackson’s and Fran Walsh’ foot in the door.
It was also unheard of to give a relatively unknown director free reigns to an unbelievably expensive film, one considered unfilmable at the time, done as a trilogy with the existence of the whole studio riding on it’s success (New Line was in serious financial trouble at the time).
I think aside from Nolan, Anderson, Spielberg and a few others (all extremely famous and great directors), something like this will probably never occur again.