From the article,
> First, OOXML was, in material part, a defensive posture under intensifying antitrust and “open standards” pressure. Microsoft announced OOXML in late 2005 while appealing an adverse European Commission judgment centered on interoperability disclosures. Thus, it was only a matter of time before Office file compatibility came under the regulatory microscope. (The Commission indeed opened a probe in 2008.)
> Meanwhile, the rival ODF matured and became an ISO standard in May 2006. Governments, especially in Europe, began to mandate open standards in public procurement. If Microsoft did nothing, Office risked exclusion from government deals.
So... maybe they weren't directly asked to open their file format, but what then? Adopt ODF which is surely incompatible with their feature set, and... just corrupt every .doc file when converting into the new format? And also have to reimplement all their apps?