Sinner, who faces Novak Djokovic in the final, first reached top spot during the French Open in June and has not relinquished it since, becoming the first Italian to achieve the feat.
The 23-year-old has won six trophies in 2024, including his first two Grand Slam triumphs at the Australian and U.S. Opens.
Sinner won his first 16 matches of the season, which boosted his confidence, and now has 64 wins and six losses this term.
Asked if he thought he could achieve the top ranking when he set out his plans for the season, Sinner told a press conference after the match on Saturday: "No, not really, because you cannot predict the future in one way.
"It also depends how you start a season. You know, if you start it in a good way like I did, you know, winning Australia, then you have much more confidence throughout the whole season."
Sinner also set the record for most wins by a male Italian player in a single season in the Open Era, spearheading the Italian movement in 2024 which also saw the rise of French Open and Wimbledon finalist Jasmine Paolini.
"I'm very proud to be Italian, and just bringing back something for the fans. They are giving me so much love," Sinner added.
"But there is not only me, there are so many great (Italian) players we have in top 100, top 200, it's amazing that the tennis is growing, and hopefully it can grow even bigger."
However, the season also included off-court problems for Sinner, as the Italian became embroiled in a doping case.
In September, the World Anti-Doping Agency appealed to the Court of Arbitration for Sport against an independent tribunal's decision in August to clear Sinner of wrongdoing after he failed two drug tests in March.
Sinner said his physio applied an over-the-counter spray containing clostebol to his own skin to treat a small finger wound and then administered massages to him between March 5-13 without using gloves.
Sinner will aim for his 17th ATP title on Sunday in the Shanghai Masters final against fourth seed Djokovic, who is chasing his 100th ATP title.
The Italian has won three of their last four match-ups, with his most recent victory over the Serbian coming in this year's Australian Open semi-finals.
"... we always had some very tough matches in the past. It's going to be a very tough one, it's one of the biggest challenges we have in our sport," Sinner said after winning on Saturday.
"I'm happy that I can play against him in the final, it's even more special, and it's very tough to predict this one."
