For Microsoft, having a full featured reliable non-core product with measurable market share is a success because it allows Microsoft to offer vertical integration without the specter of anti-trust allegations - imagine the howling in DC and Europe if Bing controlled 70% of search (never mind the valley).
Bing's robustness helps Microsoft sell software and services, while it's modest market share keeps infrastructure costs lower and Microsoft's core revenue stream coming from areas other than search reduces the pressure to game search algorithms towards their advertisers in order to increase revenue in the way that Google does.
What the article shows is not that Microsoft is inept, but rather that they are able to create an internal unit with many elements of a startup, scale that unit massively, and then transition it into a solid corporate structure capable of surviving over the long term - in other words, the article shows that Microsoft was not only able to successfully foster internal entrepreneurship in order to quickly move into a new market and capture meaningful market share in the face of a mammoth, entrenched, and powerful rival which dominated the market, but also to consolidate that position swiftly before their rival could respond in a significant way.