Leon Earnhardt transitioned to Cyber Formula after a NASCAR career that included winning the 2019 Daytona 500; he achieved this win by aggressively crashing into Phil Fritz near the end. Regulation changes for the 15th Cyber Formula Grand Prix requiring two drivers per team led to his recruitment as the #2 driver for Team Missing Link.

Driving the Strat Missionel MS-1 at his 2019 American Grand Prix debut, Earnhardt lagged considerably behind, getting lapped by Hayato Kazami. He ignored blue flags signaling him to yield, deliberately blocking Kazami and causing a collision. Earnhardt showed no remorse after the race despite Kazami's confrontation.

Earnhardt developed a negative reputation throughout the 2019 season due to repeated incidents. He caused crashes and retired from five consecutive races after his debut. In the sixth race, Kazami exploited Earnhardt's erratic driving with a tight Lifting Turn, startling Earnhardt into colliding again with Phil Fritz. His performance remained poor in the latter half, resulting in retirements during the 7th, 9th, and 10th races.

The 11th round in Japan ended prematurely under a red flag after Phil Fritz's Al-Zard NP-1 crashed violently. This race also saw Aoi ZIP Formula disqualified due to team owner Nagumo's cheating. Earnhardt participated in the final Australian Grand Prix, securing a 4th-place finish – his best result and one of only three races where he was classified.

Earnhardt continued with Missing Link for the 2020 and 2021 seasons. He showed marginal improvement during this period but remained prone to retirements and inconsistent results. A notable moment occurred in the 17th Cyber World Grand Prix where he overtook Bleed Kaga's Ex-Superion Z/A-10, highlighting the declining competitiveness of Aoi ZIP Formula following their season-long ban.

Physically, Leon Earnhardt is depicted as a teenage male with red hair extending to his shoulders and brown eyes.