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As the tech world digests Amazon’s CEO transition, it’s worth toting up all the big leadership changes we will need to follow this year.

Qualcomm president Cristiano Amon is taking over for Steve Mollenkopf, who vanquished a thousand foes and put the mobile chipmaker on a solid footing for at least a few years. Intel brought back the prodigal son, 30-year veteran Pat Gelsinger, to take over from former CFO Bob Swan, who was unable to revive the struggling PC chipmaker. And back at Amazon, as we discussed on Wednesday, Andy Jassy will take over for Jeff Bezos with the company at the height of its success but facing antitrust and labor issues.

For the current issue of Fortune, I dug into one of the biggest CEO transitions of 2020. Last April at T-Mobile, Mike Sievert took over for a legend, John Legere, who started out in last place and ended up gaining the most customers and having the best performing stock in telecom over his eight year run. Legere’s strategy combined savvy dealmaking (buying MetroPCS and Sprint), disruptive product offerings (no more two-year contracts), and memorable marketing campaigns (“the Uncarrier” and “Netflix on us”). Oh, and don’t forget the endless Twitter boasts, wars, and rants.

Sievert was alongside Legere for the whole run. The two first met in a tiny windowless conference room in Seattle in 2012 after Sievert, a boy wonder in the marketing biz, had already been interviewed by the prior two T-Mobile CEOs. Legere and Sievert hit it off from the get-go. “We sat there together and plotted an awful lot of the things that ultimately became the uncarrier,” Sievert told me when I spoke with him last month. “It was about the two of us being able to imagine the art of the possible for this company, where could it go and what would be required to get there.”

Despite Legere’s incredible run, he left plenty on the to-do list for Sievert, who was the best paperboy in Canton, Ohio, the brand manager for Pepto Bismol, and the lead marketer for E*Trade, AT&T Wireless, and Microsoft Windows before joining T-Mobile.

Now the wireless industry is just at the start of the 5G era. The networks aren’t finished, the apps aren’t there, and consumers seem confused about what 5G even means. Acquiring Sprint gave T-Mobile better airwave spectrum for offering 5G than rivals AT&T and Verizon have, but that head start won’t matter if Sievert and his team don’t build out their network and convince people to sign up. “We’re going to create some real FOMO among people carrying around AT&T and Verizon phones,” Sievert tells me.

There’s also the matter of the uncompetitive home Internet market. More than 80 million people have only one choice for broadband at home. T-Mobile (and Verizon) say they want to crack that market using 5G instead of the usual wires and fiber optic cables. “These monopolist that run these companies, they’ve never faced competition,” Sievert says, channeling his old boss. “There’s a chance to solve problems in that industry in a very uncarrier way.”

T-Mobile reported its 2020 results on Thursday and it was even better than analysts expected. Revenue for the year exceeded $68 billion, up 52%, and the carrier added 5.6 million customers.

To keep the party rolling, Sievert is going to need to plot a few moves on his own this time. He’s off to a good start.

Aaron Pressman
@ampressman
aaron.pressman@fortune.com

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