First of all, I'm not 100% sure what metric the author of that article is using for baserunning runs. The worst BsR in recent memory belongs to 2012 Billy Butler (although 2016 V-Mart is 2nd-worst. And Billy Butler is also 3rd-worst. These 2 guys are all over the leaderboard from the past 5 seasons). But this isn't just about speed. There's a lot of decision-making involved as well. Ryan Braun has really bad BsR over the past few seasons. He's still got above-average speed, he's just been over-aggressive on a poor team and has been getting himself thrown out too much. Conversely, some of the leaders in recent years - Brian Dozier, Jason Kipnis, Josh Reddick, Chase Utley, Jayson Werth - are much more opportunistic than blazingly fast.
Speed definitely helps with baserunning runs. But there's a heavy dose of good baseball smarts. V-Mart is a pretty good baseball player, but you don't get the impression he's ever dedicated a lot of time or energy to his baserunning. I think he's in the bottom 10% of the league in footspeed, but not the absolute bottom.