Another advantage the Wii had was that it had a bunch of smaller AA first/second party IPs that were absent on Wii U, stuff like Punch-Out, Battallion Wars 2, Excite Truck, Excite Bots, Wario Land, Pandora's Tower, and Sin & Punishment.
With the Wii U's tiny install base, these minor/niche franchises just weren't really viable.