The most surprising thing is the fact that you are surprised.

But in any case, is undeniable that Horizon did great.

Zelda will probably sell more LTD.

Considering the abysmal difference in userbase avalible (a 50m+ console vs a recently launched console with around 2m users) I expected it. I also expect BotW will have the better legs.

Well, for one part Horizon sold extremely well considering it's a new IP. On the other hand, BoTW is limited by install base and will possibly sell more later on

Edit: Not every game could beat Zelda even with the advantage in user base 

It begins.

I'm about 18 hours into Horizon now and spend 172 on Zelda. Horizon is great, Zelda is amazing. Zelda was a 6 hour a day game, Horizon about 2, max 3 hours a day.

Zelda will have longer legs.

Not surprising since it's selling on a new platform that has a small userbase at the moment

Yes a game that launches for a console with a 55 million userbase outsold a game that launches for a console with a 15 million user base (Wii U) and another one with 0 user base.

Yes but Horizon has been out longer and is available to a larger number of people. Something to take into consideration...

You are right  but it could be argued that you are talking about an untested New IP and 55 mill means more Games so more competion against a Franchise that is legendary  with a 97 rating and was allways going to have a superb sales ratio in regards to hardware sales.