If a user has a certain number of questions that were closed or put on hold, that user cannot ask more questions for a certain time (or even prevented from asking at all). For those with close privilege, is there a rule that say something like if you improperly close or put a question on hold, then you'd be suspended from doing so for some time? So that people won't be trigger-happy with the close button? This seems... unbalanced.
Reputation is a rough measure of how much the community trusts a user. Those voting to close earned at least 15000 reputation points between them (it takes five voters with 3000 points each to close a question). Absent strong evidence to the contrary, one should assume that the close voters acted in good faith, protecting the site from low-quality content. If they made a mistake (which happens), the reopening process is there to rectify it.
But if there is evidence of malicious voting, the responsible users can warned or suspended. If you believe you are being unfairly targeted by close voters, see this answer by Shog9.