Steve Ballmer was an underrated CEO

The specific technologies that were successful is irrelevant. Microsoft has and continues to invest in nearly every computer related technology that may come around the corner or they got late on.

The problem with Microsoft was everything went through Windows. The entire company was designed to promote Windows.

This was the fundamental flaw with Microsoft that Nadella changed. He quickly not just made Windows just another part of Microsoft’s business, to a great extent he actively devalued it.

The fact that Ballmer invested in Azure, etc before Nadella would all be irrelevant because under Ballmer Azure would have remained a red headed step child to Windows, so it’s unlikely to have seen much success under him anyways. Same goes for pretty much everything else Microsoft is doing right now.

Granted, Ballmer made the mistake of putting Terry Myerson, who headed up the failed Windows Phone effort, in charge of Windows but that's another story.

It's also a bit strange that the success of Windows was based on the ubiquity of clone PCs rather than single vendor, yet Microsoft instead tried to follow Apple here and let Google become the "clone PC" (Android phone) OS supplier.

I can't fault Balmer for at least trying to get a slice of the pie by belatedly putting out me-too products like Bing and Azure, but it's precisely because of Microsoft/Balmer missing the importance of the internet that it was put in position of being follower rather than leader.

Microsoft is really a bit like Intel in having totally dominated a product category, but then having missed on most of the major industry trends they might have been expected to lead on (for Microsoft, internet, mobile and AI; for Intel mobile, gaming and AI). They are lucky to have had a second chance with Nadella who seems much more in tune with industry trends, willing to rapidly pivot, and who seems to have made a masterful move with their OpenAI partnership in buying time to recover from an early lack of focus on AI/ML.