I checked the store on Nintendo's NA website the other day and it listed 127 games as available now. There is most certainly a decent amount of competition between Switch games, and even moreso most people have more than one console/platform, so the lack of competition argument really doesn't work so well. However, the visibility argument makes a ton of sense, and I'm curious how much that is due to the Nindie showcases, the layout of the eshop, and the news ticker on the lock screen. If those are all helping indies sell that much more than other platforms, then maybe they may have been designed to do that?
... the Wii had one of the highest attach rates ever, 9 games per console. That's a myth that needs to die.