Why?
I watched it, and enjoyed it.

Here are my reasons why I think it was so popular.

Ordinary people
Passionate people
It was not nasty, the judges, while at times brutal, where fair, and often genuinely encouraging.
In fact the judges displayed real emotion, amazing, could not contain their appreciation for the contestants.
We could all relate to it, the food was sometimes amazing, but at times it was also obtainable.
We all love a story of an underdog coming up and achieving.
It was honest, raw. Chris was the 'baddie' but this was really subtle.

There was no crudeness, bad swearing, nudity, or any embarassment in watching it.

I loved it!