How is it that “Avenue Q” won the big awards at Sunday’s Tonys? The wins were a big surpirse to everyone. “Avenue Q,” a modest musical with singing puppets playing in a small Broadway theater, had pulled off what many in the business were calling one of the biggest upsets in Tony history. There even seemed to be a sense of shock inside the producing office for “Avenue Q,” where some were nursing hangovers yesterday from a long night celebrating the show’s three victories, which included awards for best score (the show’s music and lyrics) and best book (its dialogue and structure).”