You're right that it's all speculative. The difference is what you are speculating on.

For tesla, a lot of people are speculating on something real. That Tesla will produce significant cash flows in the future, and as owners of the stock they will get those cash flows. Whether they are right will be seen.

Now there are some true tesla speculators. These are the ones who know it is overvalued, but expect someone later on will be willing to buy off them for a higher price. But still in this case, the price is tied (at least partially) to something real (Tesla's future cash flows).

I can't put the same story together for cryptocurrency. The value driven just by true speculation. That folks believe someone will buy it off them for a higher price. There is nothing else giving it value.