That was started in January 2025 so already a year ago. I see only four buildable cars being available so it hardly seems succesfull. Perhaps Mattel has been thinking “if you can’t beat LEGO, join them”. LEGO has been doing Very well with IP related properties so it could be interresting for Mattel.
You could of course be right that Mattel does not want to co-operatie with LEGO but it would certainly be cool if the CMF series 30 would be He-man