Aha! Now I get it. I just read M.G. Siegler’s post over at TechCrunch, which explains Google‘s motive for announcing the Chrome OS on Tuesday. In case you missed that announcement, Jonathan wrote a nice post about it yesterday.

Siegler said that Microsoft has plans to announce its new cloud suite of Office software on Monday at the company’s Worldwide Partner Conference in New Orleans, La. Now, this isn’t set in stone. But Siegler is looking at hints dropped by Robert Scoble on his FriendFeed account. Apparently right after the Chrome OS announcement, Scoble started talking about Microsoft’s big news, saying that it involves one of the company’s biggest products, and that it’s not the new browser, Gazelle.

Oh, you don’t know what Gazelle is? It was getting some press the other day, too. Truth be told, it’s a bit Chrome-OS-like. In an article published Tuesday on CNET, Ina Fried interviewed Helen Wang, a researcher at Microsoft, about the new project.