I thought about it too and it was a riddle for me for some time. Because user-base isn't really much bigger than on WiiU yet, but still game sales are so much better. So I guessed, Switch attracted a different user-base than WiiU, that is more willing to buy games. And I asked myself, what different user-base that is.
But then I realized something. Early adopters are such, because they are interested in gaming and have money readily available (not have to wait until they got enough together). So they probably own multiple gaming devices they are interested in. That changes the question from 'Which user-base is more willing to buy games?' to 'On which platform the users want to buy their games?'. And that solved the riddle. There was basically no reason to prefer the WiiU-version of a game over some other version. This is differently with Switch.
Here are some reasons I think might influence people to choose one version over another:
- performance: If they own multiple platforms the game is releasing on, users might decide for the version the game looks or plays best. Advantage: PC and XBox One X
- online: On online centric games, the platform offering the best online experience might make the gaming experience so much better, that this is the version of choice. Advantage: PS4 and Xbox One (especially if the free game offers already drawn people into their online offerings)
- friends: If you want to play with your friends, you choose the platform you can play with them together. Advantage: PS4 or cross-play
- convienience: You might choose the version you have the least hassle to purchase, install and play. Advantage: Switch (short play sessions without firing up the TV, play in bed etc.) and generally consoles are more convenient than PC
- mobile: There is an advantage to take your game with you. Advantage: Switch
Obviously you must be drawn into a platform in the first place. But while both WiiU and Switch might have drawn gamers with the Nintendo-games, the WiiU offered no reason to purchase multiplatform titles on that platform. Switch does.
