When it first released, Mario Kart Tour came under fire from a lot of people. Common criticisms included the initial lack of multiplayer (which has since been added to the game) and an implementation of microtransactions that some would describe as obscene. It's been over a year and a half since then and while the microtransactions haven't gone anywhere, the game is clearly popular with players and is proven to be profitable for Nintendo.
According to data acquired by Sensor Tower, Mario Kart Tour has been downloaded at least 200 million times and has generated over $200 million in lifetime revenue. It managed to accumulate $92.7 million worldwide on the App Store and Google Play from April 1st last year to March 31st this year, making it not only one of the biggest mobile racing games in the world, but also Nintendo's second most profitable mobile game.
The only other Nintendo mobile title that is performing better is Fire Emblem Heroes, which released in 2017, meaning it has had head start on Mario Kart Tour. At the beginning of 2020, it was reported that Fire Emblem Heroes had made $656 million worldwide and, within the same April 1st 2020 to March 31st 2021 time period, grossed a staggering $163 million.
Aside from individual microtransactions, Mario Kart Tour offers a Gold Pass subscription, which gives players extra content and access to the 200cc speed class for $4.99 per month. It's this pass that has purportedly driven up the game's revenue. More recently, it also added Premium Challenges. A new set of these is included with every tour and completing them yields even more rewards, but players need to spend $4.98.
Mario Kart Tour is available for Android and iOS devices.
Source: Sensor Tower