Simonsen became known in bowling fan circles early in the 2016 season, when he earned the distinction as the youngest player in history to win a PBA major championship (USBC Masters).

By age 12, he was beating some of the nation's best collegiate bowlers in tournaments, like Wichita State University alum Kris Prather.

He began bowling in professional tournaments by age 16, his entry fees staked by some fellow bowlers in exchange for a percentage of the teenager's earnings.

[9] In his first full season on the PBA Tour, Simonsen made the cash-line cut in seven of 16 tournaments, and qualified for match play five times.

The victory made Simonsen the second-youngest winner of a standard PBA Tour event, at 18 years, 11 months and 12 days.

Simonsen made history on February 14, 2016, when he won his first PBA Tour singles title and first major at the USBC Masters in Indianapolis.

[10] Simonsen qualified for two more televised finals in major tournaments during 2016, finishing fourth at the U.S. Open in November and fifth at the PBA World Championship in December.

[2] On February 26, 2017, Simonsen won the World Bowling Tour (WBT) Men's Finals in Las Vegas, NV, cashing $20,000.

[12] As one of the top eight money leaders from the start of the 2015 season through the 2017 USBC Masters, Simonsen was invited to participate in the inaugural Main Event PBA Tour Finals in May 2017.

[13] Simonsen finished runner-up to Sweden's Jenny Wegner in the 2018 Brunswick Euro Challenge, held in Munich, Germany.

[14] On August 19, Simonsen won his fourth PBA title at the Gene Carter's Pro Shop Classic in Middletown, Delaware.

While USBC and PBA rules do not allow a bowler to switch to his or her opposite hand for any sanctioned shot during a given season, Simonsen's technique was legal.

Simonsen won an additional $100,000 in the Bowlero Elite Series event on September 13, 2019, which is not counted in his PBA earnings.

[27] On February 6, 2022, Simonsen won his ninth PBA Tour title and third major at the 2022 U.S. Open, held in Indianapolis, Indiana.

The previous record holder was PBA Hall of Famer Dave Davis, who won his third major in 1968 at age 25 years, 343 days.

Two weeks later, Simonsen qualified as the top seed for the PBA Dave Small's Jackson Classic, but lost the March 9 championship match to E. J.

He became just the fourth player (after Dick Hoover, Billy Welu and Jason Belmonte) to successfully defend a title in this event.

[32] On July 30, 2023, Simonsen won the Storm Striking Against Breast Cancer Mixed Doubles event with partner Danielle McEwan.

[36] Simonsen rebounded two weeks later, climbing the ladder from the fifth seed in the TV finals to win the PBA Pete Weber Missouri Classic.

He went on to face Group 1 winner Marshall Kent, who had defeated Simonsen in the title match of the Tournament of Champions earlier this season.

[39] On July 28, Simonsen and partner Danielle McEwan repeated as champions at the Storm Striking Against Breast Cancer Mixed Doubles event.

[41] For the second straight season, he finished runner-up to E. J. Tackett in the Chris Schenkel PBA Player of the Year vote.

Simonsen was the subject of a Rolling Stone article in January 2024, titled, "Meet the Gen Z Hothead Burning Up Pro Bowling".