Wait, are you suggesting that Microsoft didn't bribe a dozen counties, at a hundred or more people, and pull off the biggest corporate cover-up in history (aside from the brilliant and astute readers of Slashdot who have worked diligently to uncover this plot) just so they could get their document format adopted as an ISO standard--something which will yield them little to no gain because the market share of Office essentially requires competitive document compatibility?
Actually it gains them a lot. For one thing, as reported here, in at least some of the nations where irregularities have been seen laws were recently passed requiring all government documents to be published using open standards. Since MSOffice does not provide this facility, they'd have to use something else to produce the documents. If they can just say their document format *is* an open standard (ipso facto!) they don't lose their coveted market share and they don't have to make any changes to their software.
It also gains them something in an area of Microsoft's desires that has puzzled me forever. For some reason it just offends their sensibilities to support ANY open format in their software, be it png, OpenDocument, or XML. HOWEVER ever since the Linux revolution around 2000 and the big hoopla over open standards Microsoft has billed themselves as the most open company in the universe out of one side of their mouths while deriding the Free Software people as Communists out of the other. In any case this is one more feather in their cap of features in their Software they can point to and say "See we're the most open company in the world!"
This is, in fact, what started this mess. Microsoft claimed they supported XML, an open standard, in their office suite, people with more than half a brain said "that doesn't look like XML to me" so Microsoft decided to call what they were doing OOXML and get it approved as a standard. When that did not fly, the votes got changed so it passed.