BOTW does well because its appeal is not limited like prior games, the problem in older games was that they were centred around dungeons and this dictated their appeal as the games were built around them. BOTW however put the focus on Hyrule as a whole turning it into the focal point that the game is built around this meant new kinds of mechanisms for gameplay and progression could be explored.
The result is the appeal widen massively as factors that stopped many people enjoying the prior games have been addressed this is why older games aren't selling like BOTW it's not that they're only BOTW fans it's that the older games do not have what has drawn in new fans. We've seen this with other big franchises like GTA for example, CTW which was like a modern version of the older games did not sell anywhere near the games that are like GTA3.
It will be the same with future Zelda games the ones building on BOTW'S approach will sell very well. For reference look at videos for BOTW online and look at videos of older games you're going to notice a world of difference in the type of videos you find.