Executive Committee of the Ruling Class
As Adam says,
we should expect the capitalist powers-that-be (corporations and governments) to oppose any monopoly that affects an input to production, as "office productivity software" clearly does. Capitalists will also make a point of preventing any one of them from acquiring much more wealth than the others, hence Microsoft is a prime target for them.
That was a major point in Baran and Sweezy's description of how the state functioned as executive committee of the ruling class, in Monopoly Capitalism. Because the state functions in the interests of the corporate economy collectively, it acts to rein in specific corporations or industries when they hurt the collective interests of organized capital. When low rates of profit in some industry threaten the economy as a whole, likewise, the state intervenes to create a floor (as with agriculture and the extractive industries).
It's interesting, in this regard, that so many of the major anti-trust actions of the U.S. government have involved resources or infrastructures that were centrally important to the corporate economy as a whole: Standard Oil, AT&T, Microsoft.... It's also interesting that the industries most prone to nationalization under the so-called "social democracies" are those very same resources and infrastructures, which the large corporate interests may prefer to manage collectively through the state.