But on Friday Microsoft briefly reclaimed the crown as the world's most valuable publicly traded company, a position it hadn't held since 2002. At close on Monday, it had slipped into third place behind a resurgent Apple and rising Amazon , but all three companies are essentially battling it out for the top spot. Whatever Microsoft's precise position, it's certainly relevant again.

Over the weekend, a 2007 blog post entitled "Microsoft is Dead" from Paul Graham, co-founder of Silicon Valley start-up factory Y Combinator, was recirculated online. Graham argued that while Microsoft was still making money, no one was scared of it anymore.

Amid the renewed discussion of his blog post, including on Y Combinator's Hacker News discussion forum, Graham weighed in on Twitter. He said founders he's spoken with still aren't seeing Microsoft as the competition, but he also acknowledged that the company is in better shape now.

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There are several reasons for Microsoft's resurgence. And a lot of it can be traced back to early 2014, when the company replaced Steve Ballmer with the more soft-spoken Satya Nadella as CEO.

Under Ballmer, Microsoft stock largely went sideways. But under Nadella, who took over in early 2014, Microsoft stock has moved up and to the right, consistently outperforming the S&P 500. On Monday Microsoft stock was trading above $113 per share. It closed at $36.35 on the day Nadella became CEO.

Here are several specific ways that Nadella's leadership has helped Microsoft get back on top.

From Windows-first to Windows-and. The old Microsoft was obsessed with maintaining Windows at the center of all computing experiences, and that sometimes got in the way of what customers wanted.

Under Nadella, Microsoft set aside Windows for smartphones and brought greater capabilities to mobile operating systems controlled by Apple and Google. Its engineers contribute considerably to open-source software projects, and the company regularly makes its own software available under open-source licenses. While it is still the Windows company, it has embraced open-source Linux, in the cloud, in Windows 10 and even in the realm of patent enforcement.

Doubling down on cloud. With Nadella leading Microsoft has gone from being just another provider of public cloud resources to a real challenger to market leader Amazon Web Services.

While Microsoft was active in the cloud under Ballmer, Nadella has made cloud a higher strategic priority and changed compensation for salespeople to ensure that customers ended up using Microsoft's cloud services.

Nadella has drawn investors' attention to a metric Microsoft calls commercial cloud -- which includes the Azure cloud as well as business subscriptions to Office 365 productivity tools, commercial LinkedIn revenue and the Dynamics 365 business software -- by disclosing quarterly revenue for the category.

And he has held steady on capital spending, which has made it possible for the company to open many data centers around the world.

In an October note to clients, Griffin Securities analyst Jay Vleeschhouwer estimated that in Microsoft's 2019 fiscal year, Azure will produce $12.8 billion in revenue -- more than 10 percent of the revenue Vleeschhouwer expects from Microsoft as a whole for the fiscal year.

More open to partnering. While AWS continues to compete with some customers, Microsoft has tried to make itself out to be less of a threat and more of a collaborative partner.

At a Credit Suisse conference last week, Microsoft executive vice president Jason Zander was asked about what makes Microsoft's Azure cloud unique. Zander pointed to the breadth of Azure's portfolio and its ability to work alongside companies' existing on-premises data centers. He also talked about how Microsoft thinks about its own customers.

"One of the key things I always tell potential customers and partners, we're not your competition," he said. "We're here to help support you in a world where I think a lot of customers that I talk to -- they don't want to get technology on one hand from a provider and have that provider turn around and compete with them on another."

With Nadella at the helm, Microsoft has also been willing to put aside longstanding rivalries. It has formed partnerships with competitors like Dropbox, Red Hat, Salesforce and even Amazon.

Less reliant on personal information. As some business executives and public officials talked about regulating big technology companies, Microsoft has largely been insulated from the strongest criticism.

While Microsoft still has an online advertising business through its Bing search engine and MSN family of web sites, its core business is elsewhere. That means Microsoft has less obvious incentive to collect and store data about users.

Facebook, by contrast, has seen its stock fall considerably this year after numerous questions and scandals related to how it uses and secures information about its uses.

"I think that until Microsoft has been caught doing something really bad with data, they have a huge advantage," early Facebook and Google investor Roger McNamee said on CNBC earlier this year.