There was a craze for monster stuff in the early 1960s. I was there. It was the result of several things:
1.) the rising population of Baby Boom kids. as i have ranted before, the peak of the Baby Boom was the mid 1950s, even though in media presentations they act as if the boomers from the start of the book dominated. In reality, some Boomers weren’t born until the early 1960s. In any event, you had a vast new population of kids that were mostly about 5 in 1960, with others down to zero and going up into the early teens. Prime population for viewing the 1940s and 1950s vintage horror films – not too intense, effectivelt G-rated, but interesting and unusual enough to capture their interest in a way that romances and war dramas wouldn’t.
2.) The release to television syndication of the “Shoch Theater” package in the late 1950s that put a lot of old Universal monster flicks on TV. All those Boomers could watch monsters on TV for free
3.) At the same trime, the cheapo 1950s horror and sci-fi flicks made for drive-ins and the like were available for local TV broadcasts. There were cheap Japanese films like Rodan and Godzilla, too.
4.) The rise of specialty magazines like Forrest J. Ackerman’s Famous Monsters of Filmland, that excited interest in these films and helped produce an audience.
5.) The still-burgeononing TV market, especially local channels in need of cheap and plentiful programming. You can only fill so much with reuns of Love that Bob, The Gale Storm Show, and I Love Lucy. The stations were too poor to finance their own soaps or talk shows, or to buy more recent films. So you got a lot of Three Stooges, You Bet Your Life, Cartoon shows with Kiddy hostas, and “Creature Feature” or “Chiller Theater” or “Supernatural Theater” or whatever.
Once this gets going, other elements feed on it. With a market for monster flicks, you get licensing of Universal monsters to Aurora Plastics, and model kits appear. With Frankenstein and Dracula popular, you get The Munsters. In response, you get Ther Addams Family, and so on.
See David J. Skal’s books, especially The Monster Show. He calls this 1950s-1960s boom “Monster Culture”