The past week had been tumultuous for Boyle. She lost her cool during a confrontation with two reporters, and the police intervened. Another contest judge said Boyle had contemplated pulling out of the program to soothe her frazzled nerves.
On the night itself, she appeared on stage composed, in a glamorous but modest sparkly floor-length dress and gave a polished performance, but it was not enough to secure her victory.
Millions voted by telephone after Saturday's live show, which Boyle had long been expected to win.
"She lost because people didn't bother voting for her because they thought she was going to win it," lamented 21-year-old Gordon Mackenzie. "I didn't vote for her because I thought everyone else would.
Her hometown of Blackburn, Scotland - a working-class village about 10 miles (16 kilometers) west of Edinburgh - rallied round her, stringing up signs declaring their support. Her defeat was greeted with shouts of "no" and gasps of disbelief at the Happy Valley Hotel, where neighbors and friends had gathered to watch the program.
On Sunday Scotland's First Minister Alex Salmond was scathing of the media pressure that Boyle had almost buckled under.
"We've got elements of a press who like nothing better than to build people up and then drag them down," he said on BBC's Radio Five Live. "It's pretty sad actually. It's almost a psychosis. I would love Susan to win, to triumph over that sort of nastiness."
Boyle became an Internet phenomenon after she auditioned for the television talent show. She was up against a host of everyman acts determined to find stardom on reality television, including a 12-year-old whose voice was compared to Michael Jackson's, an 11-year-old body-popping dancer and a grandfather-grandaughter singing duo.
For the finals, she returned to the song that made her a YouTube sensation, "I Dreamed a Dream" from the musical "Les Miserables."
Boyle's entree into the limelight has become reality-show history, after being viewed millions of times - the fifth-most watched clip ever on YouTube.
But despite her popularity, she was beaten in the finals by the street dance group "Diversity," which mesmerized audiences with a frenetic but perfectly choreographed dance routine . Judge Simon Cowell said their performance had been "utter perfection."
"Diversity", made up of 11 friends, including three sets of brothers, from Essex, east of London, were never seen as front runners even though they had won praise throughout the competition and had won the UK dance championships in 2007.
On Saturday, they looked stunned as they heard they had beaten Boyle.
Boyle was quick to praise "Diversity" saying "the best people won."
Dancer Terry Smith, 24, returned the compliment, saying Boyle is bound for a great career.
"Diversity" have now earned them 100,000 pounds ($159,000), and the right to perform for Queen Elizabeth II at the Royal Variety Show in December but Boyle may well have the more lucrative future.
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