Batman Begins) were the first of this new era of superhero films to be incorporate a serious setting, not really relying on fantastical plot devices.

I think you mean Spiderman 1 or Xmen...

Batman Begins just follows the more grounded approach to comic books, they started. Not to mention, Batman Begins uses Batman's more surreal/fantasy villains in Ra's Al Ghul and the Scarecrow.

people thought you had to be either 11 or a total nerd to know anything about comic book superheros.

This isn't really true either. Batman and Superman fixed this in the 70's/80's. Comic books became their most popular and most established in pop culture in the 90's man.

The reason why modern day comic book movies started, was because the major comic books became established fictional characters. They started with the bigs dogs, Batman, Superman, Xmen and Spiderman. That run of movies, proved that comic books were financially viable

And that bled into Daredevil, Punisher, Catwoman, Fantastic 4, Elektra, etc etc.

So yeah, Nolan's Batman trilogy was just hopping on an already existing wave. Same with Iron Man, Captain America and Thor. But that all caused a oversaturation of mediocre and really straight up bad movies. People were losing interest.

However, The Avengers and TDRK(sequel to the most popular comic book film ever at the time) released in 2012 and comic book movies haven't waned since.