You need to take in account huge difference in user base between Switch and XB1/PS4 when you talk about sales of those games. Obviously you didn't pay attention on Switch news, actually most 3rd partys (2K, Ubisoft, Namco Bandai, SQ, Capcom...) said they are satisfied with sales of their games on Switch and that they will announce more games for Switch, few days ago we had Nintendo France said that EA is very satisfied with Fifa sales and that they said they will bring more games, also few days ago Bandai Namco said that Dragon Ball Xenoverse 2 for Switch sold more than 500k already and that actually passed Steam numbers, so I wouldn't pay attention too much on VGChartz numbers. I am pretty sure that Bethesda this month when they have quarter results will also say they are satisfied about with sales, especially because Skyrim is actually best selling multiplatform game on Switch in US in 2017.
For the record, multiplatform Switch game dont need to sale same like on XB1/PS4 in order that 3rd party is satisfied with sales, hardly that any big party have expectations they will have similar numbers on Switch, but they can make quite profit even with lower sales, and all pointing that 3rd party games are selling good and much better on Switch than on few previous Nintendo platforms, for instance it seems that Fifa on Switch fastest selling Fifa compared to any other Nintendo platform (it even sold better in Japan than Fifa on PS4 despite huge difrence in instal base). And point is simple, games on Switch have extra value beacuse they offer full home console and full handheld play, for instance you can bet some people will buy Switch only to play games like Skyrim, Doom, Dark Souls...in full handheld mode, and that wasnt case with any past platform, and thats why 3rd partys are now selling better on Switch compared to previous Nintendo platforms, and 3rd parties also seeing that.
I actually think that most 3rd parties decided to support Switch with much more games only last few months after they realized that Switch is seling great and that 3rd party games are selling good on it, and porting of course can take time, espacily developing brand new game. So we will have much more 3rd party announcements how time pass in any case.