This fake news phenomena is simply the natural progression. Media has always been caught between the need for speed and the need for quality, with each outlet at any moment falling somewhere on the spectrum between those two goals. Too much of one extreme usually spelled the disaster for the outlet, either because it became too elitist, or if became too ridiculous. And starting a new media outlet represented significant effort and cost, and the distribution channels (print, TV, radio) were relatively expensive.

In the era when the media channels themselves are extremely cheap (i.e. the Internet), the extremes are not as dangerous as they used to be, and risking going to extremes became much more valuable. However, with the cost of channels gone, the cost of quality becomes a much more significant burden, and optimising for speed became much easier, at the cost of quality. Add on top of that the willingness of various groups to pay for the costs of such media (optimised for speed as opposed to quality), it is clear where such abundance comes from.

Note: By "media quality" I mean an amalgamate of different elements like topics covered, quality of writing/reporting, production quality, amount of research etc.