I keep referring to ‘The Glut’ that occurred in the B&W comic book markets in the late ’80s, and came across this great series of re-posts from the Comics Journal. Of course, I cannot re-post the whole thing, but here is the pertinent page from the article, one that explains it all perfectly.
I highly suggest anyone trying to understand just how the heck the comic book industry destroyed itself once upon a time read the whole thing over at The Comics Journal; http://classic.tcj.com/history/a-comics-journal-history-of-the-direct-market-part-two/
From A Comics Journal History of the Direct Market, Part Two by Gary Groth.
Black and White and Dead All Over
(Originally published in The Comics Journal #116, July 1987; reprinted in The Comics Journal #277, July 2006.
The bloom was off the rose in December  or, if you were slow about it, January of last year . What rose, you ask? The most sacred and cherished rose in America: the belief that the American public will consume limitless quantities of useless garbage.
This idea ran afoul of a very basic economic reality: you cannot shovel shit into a finite market forever. The profiteers who jumped on the black-and-white comics-publishing bandwagon within the last year learned this when the black-and-white comics market collapsed. (The ripple was felt in the market for color comics and other formats, too.) From December through April at least, publishers have reported a drop in sales from 15 to 50 percent across the board. (That means even comics you may have thought were rock-solid have suffered.) The sales of some black-and-white comics may have plummeted even more dramatically over the four or five month period. The cause of the glut and subsequent collapse was partly greed and partly passivity on the part of “publishers,” distributors and retailers. One must wonder why, with all the breast-beating of the distributors and the ballyhooing of the innumerable trade shows held all year, there wasn’t a single mechanism within the entire infrastructure of the direct-sales system that could have foreseen or mitigated the disastrous economic collapse. Part of the explanation is that the infrastructure’s primary purpose is to create a self-perpetuating consumer frenzy at the expense of any responsible or even sane sense of proportion.
The crash began as a boom and the boom was in black-and-white comics. You would’ve had to have been particularly inept to publish black-and-white comics in 1986 and fail. As nearly as I can piece it together, this is what happened: