0-6 is certainly a surprise. Losing the way they did today is an even bigger surprise, which can't be explained.
However, to me overall the biggest surprise is not this season but last season. I looked at that team last year and I couldn't figure out how they were doing it. There was no particular formula to all those games they were winning. I thought it was a tremendous coaching job by Fisher, and it reminded me a little of Bill Cowher's coaching jobs in the mid 90s. This season reminds me of Cowher's Steelers who collapsed in the late 90s (though those teams never started out 0-6).
In the end, like with Cowher's Steelers before the arrival of Big Ben, it is very difficult to win in this league without an elite QB. A good defense and a running game can only get you so far, and the problem is there are usually too many workable parts to that equation, so if a few of them break down (like a couple linemen get hurt or a defensive star leaves, etc.) everything falls apart. Unless you have that QB that can keep you winning through the injuries. If you're stuck with a journeyman or a draft bust, your chances of success are dim.