The problem is, Nintendo HAS to take action against initiatives like these. That japanese kart company has been profiting using Nintendo’s mascots for several years. In fact, a few years ago, they were called MariCar and Nintendo contacted them and told them to cease and desist, or face legal consequences. They ceased and desisted… under the MariCar name, and kept going at it as Mari Mobility.
You can’t say they didn’t actively look for trouble. Nintendo are forced to enforce the copyright laws of their own properties, or they risk losing the rights to them. That’s how law works, generally speaking.