Generally the average consumer found Wii U more confusing than Xbox One. But Microsoft basically followed off of "360" so they had a safety net. If Xbox One came after the actual Xbox 1 well...uh...
Only thing that naming it Xbox One caused was making it hard to find original Xbox stuff for a year and a half.
Wii u however had more than the name against it. I mean the marketing was a complete failure for way to long.
I think the first major event didn't even show the tablet it just showed a Wii U on the side at a weird angle and comments thinking the consoles was actually just an original Wii starting the add-on rumors.
I think it was more that the large Wii casual audience had abandoned the Wii by the time the Wii U released. Maybe they were more enamored with mobile games by then or whatever, and the Wii U had nothing with the wow factor of Wii Bowling to bring them back on board.
MS has been known to artificially bump up version numbers to make a technology appear more mature than it is. That's why they didn't want an Xbox 2 competing against a PS3, so they named it Xbox 360. So it's baffling that they'd name their 3rd version "one"