They say that Apple disrupts markets.
At least that's what the legends tell us. Cupertino marches in, creates something that is a little different, looks a little different, does something a little different, or is merely oddly understandable to a real human being.
For many real people, the iPad was something the likes of which they had never seen before or ever really imagined. Within an instant, it took over a market and became that market: the iPad market.