Problem was they were trying to replace symbians sizable market share with WPs nonexistant one.
The problem is focusing on 12 months of data for a decision that set the path for that division for a decade or more.
RIM, through at least mid 2010 also had a very solid looking chart, if you projected it straight forward. They did not do the 'burning platform' thing, and have performed almost as badly (likely hard to choose which company looks worse, depending how you measure). Both companies enjoyed massive sales of legacy products which were certain to fade.
Nokia is at least 12 months ahead of RIM in transitioning to a long-term viable OS. Given the massive uncertainty about RIM in the corporate world, and the initial promise of WP7, I would classify Nokia's decision as high-risk/high-reward, but definitely defensible. iOS and Android are leading the charge, but there is certainly room for a more productivity-focused OS to beat them in a number of market segments.
There will be a time for reckoning, but that time is likely no sooner than Q1-2014, unless we are considering HP as an example worth repeating. I.e. A solid platform given about 6 weeks to shine and then dumped.