Market Creation and Development
Microsoft has always led the pack in market creation and development. Regardless of technical superiority, MS has consistently provided solutions, or provided avenues for 3rd party solution development. Their leadership built lots of things - from a PC in lots of homes, to wide spread Internet browsing, to high performance computing applications, and to Open Source Software. Without MS there would not be many user friendly (non-command line) options for using a computer. And the best part is the most useless people are going to trash me for what I said because they like command lines: unfortunately they aren't part of business...
It only makes sense that MS will get some traction in HPC. They've gotten traction for themselves and many, many others in the past so this is just another opportunity to raise the bar in usable computing - which includes vendors, channels, developers, sales, and most important - USERS. Doesn't matter what's "best" you must please a significant portion of your users. Failure to do so leave you standing all alone with an unwanted product - sort of like lots of IT professionals have been left standing all alone with their willy in their hand and no one to use their product. It's marketing and partnerships that make products. Everything else is a technical issue that can be solved one way or another.