I don't think it stems from really increasing the author pool so much as reducing the amount of effort put into editing the material. A good editor can dramatically improve legibility, but few bloggers are paying for it.
You raise an interesting point, but the purpose of an editor is to filter content before publication in a scarce medium so that resources aren't wasted publishing crap no one wants to read. The editor serves the owner of the means of publication and acts as a quality filter so that only content worth buying and reading will make it into print.
Unlike a printing press or a broadcast frequency, the internet is unbounded and access is dirt cheap. There's effectively no cost to publish crap, so there's no reason not to wait until after publication to filter for quality.
Editors do both. However, if you look at the standard quality of a small town newspaper from the 1920's the overall quality is not all that high. Realistically, papers like the New York Times are an outgrowth of having a huge audience which can support a lot of staff, but there used to be a lot of small players out there who had a lot less content to choose from.
