Established car makers have businesses that are easier to predict. They’ve been operating for a long time and you have a pretty good idea what “doing well” or “doing poorly” would look like for them. A much newer company like Tesla, which is based on emerging technology, does not have so well-understood of a future. There’s a lot more unknown about how big it might become.

Most times, this is seen as big unknowns and risk, therefore investors are wary. But Tesla has had enough real world success to be encouraging, yet is still new enough to enjoy “we don’t know how big this thing will get” speculation. Basically a lot of people think it’s a reasonable bet that Tesla will be huge in the future. Therefore their stock has high demand.