Pawlenty didn't fail because "Unfortunately for Pawlenty, the GOP zeitgeist doesn't seem to support nice guys, when niceness is their most salient attribute." It would be better to say that Pawlenty failed because he treated Republican primary and caucus voters like yokels. Do we really have to go back over the time when he called on conservatives to take inspiration from an act of alleged domestic violence? Is that nice? Was it "nice" to try to weasel out of having to give an answer on waterboarding? Was it nice to coin Obamneycare when Romney wasn't around and then weasel when asked to defend the term to Romney's face?
Pawlenty's economic record as governor and his stands on social issues made him a good fit to run for President. Pawlenty didn't run as that guy. He ran as a guy who seemed to "learn" everything he thought he knew about conservatives from reading hostile accounts in liberal-leaning media outlets. For all her flaws, at least Bachmann understood that filing a bill to repeal Obamacare was closer to the desires of right-leaning voters than talking a bunch of nonsense about taking a nine iron to Obama's agenda.
There is more than one reason why Bachmann showed greater appeal among conservatives than did Pawlenty. One of those reasons was that Bachmann showed them respect, while Pawlenty showed them condescending obsequiousness.