I don't follow Microsoft closely enough to really determine which decisions are influenced by Nadella, but I do think that it's a very good question to ask. Windows is one of Microsoft's mainstays, and Windows 10 issues have been going for a year without any apparent action from the top. If Nadella can get praise for the good moves (which seem to be driven by lower-level decision-makers, but enabled by Nadella's policies), then he should also be held to account for the failures. Even leaving aside any responsibilities to customers, Windows is both a key product and brand for Microsoft as a shareholder-owned company, and those assets are taking ongoing damage right now.