Going back to the topic of how the monster era started, there is a very interesting
4 page introduction by Dr. Michael J. Vassallo at the beginning of the new Tales of
Suspense Masterworks collection.
From the solicitation of Tales of Suspense Masterworks:
In 1958, Atlas Comics Editor-in-Chief Stan Lee was joined by two titanic talents: Jack Kirby and Steve Ditko. Together this trio of storytellers launched Tales of Suspense and its sister title, Tales to Astonish, and along with them the beginnings of a creative revival that would change comics forever.
Kinda wish I knew more about this era, but it looks like Atlas imploded in 1957, and
the combo of Stan, Jack, and Steve clicked the year after.