Let's not go pretending that any game released on Switch is guarranteed sales to supposedly desperate Switch owners.  If that was the case, VROOM in the Night Sky would have half a million downloads or more.  Any game that releases within a month of a console's launch has an advantage of a small library to compete with.  That's true for any console.  But, the game has to be good as well.  It's a good game, and it lent itself well to the Switch's portability.  These are the factors that led to it having more sales on Switch than anywhere else.  Not just "that it was there".

It's good to see these games doing well somewhere. I think the PS4 and Xbox crowd had poisoned the well for indies due to incessant console warring. When fanboys were trying to douse their value against the major releases, and therefore, too many people started acting too cool for school toward them. Games like those are great for handhelds and its good to see Nintendo gamers are willing to branch out towards them. It's a new place where the games can possibly thrive instead of getting lost in the Steam shuffle.

I think 15-20 hours is a good length for a game to become not too boring. In fact I think Yooka Laylee is a perfect game to play while watching something else or while the girlfriend is cleaning the apartment. Also I've seen a decent progress with their patches.
Wonder Boy is probably a bit more challenging in that regard and needs more attention.

I'm completely fine with better games being more expensive, but there will always be a point where I can't accept it any longer.
Even a game that lasts 10 minutes but has the best gameplay in all of video games wouldn't be worth $10 to me. (extreme)
Also I'm buying far too many games this gen. I can't afford to buy a game for 20€ and then only get a few hours out of it.

Of course I'm only saying that because I know that Wonder Boy 5€ and Yooka Laylee 15€ are realistic prices that won't even take that long to reach.
Yooka Laylee is also available on retail and thus falling in price quickly. I'm buying my digital games through foreign Xbox stores (mostly Brazil) where Wonder Boy costs already 10.50€ without any discount applied. In a year it will probably see a 50% discount, thus being around 5€.
Yooka Laylee is available digitally as well, but I prefer a physical version.

Awesome to hear that lots of Switch users are buying these indie games. It seems to be working by a lot!

This bodes well for Switch's future.

I don't disagree, but I wasn't commenting on why the Switch version sold the most, just on the topic of concentrated libraries.

I think that a lot of gamers who yearn for the cartridge-based retro-gaming feel may end up going for the Switch. I think it'll be cool if there ends up being physical releases of a lot of games like this.

That and the idea of being able to suspend and resume at any time, in any location is too fantastic. to resist

Yeah, that's also a nice addition!

Potentially any 2D graphics game is a better fit Switch.
Thats's simply because you don't have any particular reason to play it on a high-end hardware, portability is a much stronger advantage for the player in this case.