That's because Tesla are massively overvalued relative to what they will most likely achieve. Tesla are not the largest car manufacturer at all - Tesla's market cap is hugely bigger than ford's, but ford's yearly revenue is only a bit smaller than Tesla's market cap
Companies are valued based on what people think they will do in the future. And many people think Tesla will cause a revolution in the car industry developing the technology to eliminate combustion engine vehicles from the roads. As they mentioned today, if they achieve what they're aiming for in the next ~3 years, electric vehicles will be cheaper in total cost of ownership than combustion engine vehicles.