I don't think the two fields, although they both relate to entertainment, correlate directly. Bands went under because tastes changed from rock towards hip-hop. There are other reasons that the number of live venues had declined, none of which I'll go into here.
There are still a lot of bands that primarily use the internet to get their music to the people, so that has changed. But the decline in garage bands is more due to a major change in music tastes, which is more generational than based on the method of delivery.
In publishing, the venues increased via independent book publishing after Amazon opened it up in 2007 or 2009 (don't recall the exact year off the top of my head). There are also other venues available for independent authors to get their product out there. This opened things up for the publishing equivalent of 'garage bands', and many have become quite successful because of it.
James Patterson writes the kind of stuff that's been around for years. What he did was change how books are advertised, and he also started using ghostwriters and co-writers to push more product out there -- something that may have already been done before but perhaps not so blatantly. EBooks and electronic publishing have undoubtedly added to his bankroll, but he was doing well even before the shift to internet book publishing.