didn’t take off until Tesla built a Gigafactory to supply their batteries
BYD doesn't rely on Tesla to supply their batteries. It's the other way round: BYD started out as a battery company, and Tesla relies on their batteries in Shanghai, Germany, and other factories. Tesla originally used batteries from CATL, another Chinese company, but started switching to BYD a few years ago.
Thought this was about Valve's Artifact TCG, and was like "wait, didn't they already shut that down?"