Tesla are doing OK now, (kind of) breaking even, and making a decent number of cars. I think most would agree they're more solid now than ever before, and it seems like they're probably here to stay. But much more importantly we have to look at what they could be doing in 5-10 or 20 years.
Often people say Tesla isn't anything near the behemoth that is Toyota (true), and their stock shouldn't be higher than Toyota's. Toyota now make just under 9 million cars per year worldwide [1], exactly the same as they made in 2007.
In 2007 their share price was ~$75USD and now it's roughly similar. While they make a ton of cars and are profitable, they're not growing or really doing anything drastically different to almost 15 years ago. It's very likely in 10 or 15 more years they'll still be trundling along, doing the same things, making a similar number of cars. That's solid and good, and their stock price reflects that.
Tesla, on the other hand, are going all out for expansion. With the new factory going up in Germany, and one about to be announced in the USA for Cybertruck, it seems like they have no intention of slowing down, and plan to continue to grow extremely rapidly. In 10 years they may be making as many cars as Toyota is now. In 20 years they might be twice the size of Toyota (in terms of units produced).
Whether you believe they can pull that off or not is a matter of speculation that isn't worth getting into. That "guess the future" is exactly what we're seeing in the stock price. Toyota's stock price is not skyrocking because they're not doing anything radical, and aren't growing exponentially. On the other hand Tesla's stock price is skyrocketing, which we can read to mean a huge number of investors think they can pull off massive growth.
Of course time will tell, and in the mean time we can all gamble on what we think will happen.
(Note - I haven't even touched on Tesla's plans for self-driving, their "revolutionary" new battery chemistry, home storage, large scale storage or whatever else they're (maybe) cooking up. Also important is the inevitable extinction of the internal combustion engine. Those are heated topics of disagreement, but again, the fact the stoke price is climbing so fast shows people think Tesla have a very bright future)
[1] https://www.statista.com/statistics/267272/worldwide-vehicle...