When Yu Kaicheng first started talking about world models in 2023, the response he kept getting was that the field was too far away, even fantasy. Three years later, with Fei-Fei Li, Yann LeCun and a stream of new entrants raising billions, world models have become the physical-AI narrative of the moment. Yu, by then already a world champion on ECCV's autonomous-driving track and number one on the Fail2Drive benchmark, did the least intuitive th…