Do you know how many votes you need to finish 12th when only 137 people voted? Not many.
Maybe it went something like this:
1. Lebron James 40
2. Dwight Howard 35
3. Kevin Durant 30
4. Kobe Bryant 7
5. Derrick Rose 6
6. Chris Paul 5
7. Dwyane Wade 4
8. Steve Nash 2
9. Blake Griffin 2
10. Deron Williams 1
11. Pau Gasol 1
12. Rajon Rondo 1
13. Eric Gordon 1
14. Ricky Rubio 1
15. Andrew Bynum 1
If anything though, I'd imagine the SI questioner to players went something like: "List in order, the top 3 players you'd want to build a team around." Like an MVP ballot.
I'm sure LeBron, Dwight, and Durant were 1-3 on most people's ballots. Also maybe the questionnaires were sent to someone in the team office, who distributed it to players, so maybe somebody in the Lakers and Suns organization made sure every player filled it out (hence 3 Lakers and Steve Nash) while other organizations like the Knicks and Mavs probably blew it off. Some players are probably loyal to their current teammates too (I wouldn't be surprised if someone on the Hornets voted Eric Gordon, and purposefully didn't vote Chris Paul out of spite). Really Rondo probably got like two or three 3rd place votes, or maybe one 2nd place vote at best. And maybe that one vote came from Big Baby or Nate Robinson or Sasha Pavlovic, not the kind of players you're hoping want to play here with Rondo.
This is like when PJ Brown and Marcus Camby both finished 14th in MVP voting in 2005, each getting one 5th place vote. It does not mean either were the 14th best player in the NBA.