theres a good explination in autosport, some f**king clever people out on the pit wall!
Exactly, it was a well calculated risk taken by Ferrari but unfortunatly for them the tyres came back to other drivers which delayed there pit stops till further in the race and thats what ruined Alonso and Webbers race.
It would have been a miscalculation if Ferrari had calculated the tyre de-grading process over time which over a track that is constantly developing is impossible. No one could have calculated if a tyre would degrade and produce slow lap times then "come back to life" and be able to put in fast times again 
but anywho, luck of the draw and Vettle won it, if the other teams catch up technically for next year Vettle has no chance! 
jesus , this is like a semantics competition.
Noun 1. miscalculation - a mistake in calculating
mis estimation, misreckoning
error, fault, mistake - a wrong action attributable to bad judgment or ignorance or inattention
when webber pitted he was still going to come out behind rosberg, petrov and kubica who had already pitted. webber needed to pass all of them to win the championship. If ferrari had ignored webber who was going to be out of contention anyway and kept an eye on what the real competion (vettel) was doing they might have stood a chance. they focused on the wrong man.
whatever way you try and twist it , ferrari made an error (what me and the dictionary would also call a miscalculation) which helped Vettel win the WDC.
Magic F1 fairies didn't sprinkle his car with lucky winning dust.
