They thought millennials wanted "shorter" based on the success of tiktok/instagram/etc. But their content was too long to be short. And the "golden age of TV" we are in basically proves that people don't really want shorter in scripted content. If anything, we want deeper stories. Novellas have never outsold novels. Movies were an outlier for a while, based on the fact it was so hard to produce content, but even movies are now becoming trilogy's+. Youtube is hugely successful because it satisfies niche content, the length is irrelevant.
They thought it should be "mobile", but by limiting it to mobile they meant that you could only watch part of the time. Netflix is perfectly fine on mobile.
The switching back and forth thing feels like a novelty like 1 time then you just do whatever you want and stick with that. Its also hard for creators as you don't know how people will use it, so you have to make it "worse in landscape" and "worse in portrait" so people can watch on either method.
I absolutely LOVE people taking big risks on ideas. This was just a bad idea from the start. I wish they would have blown $1.8B on some shoot the moon healthcare idea or something.