The big problem for Tesla is scaling up. Producing the model 3 at scale at a 40k price tag is much harder than anything they have done so far. It has taken competing car companies decades to get to the point where cheap reliable cars just roll of the factory line. Just quality control alone is a huge problem at scale. Sourcing all materials at scale is enormously difficult. In manufacturing scale is everything.
In terms of interior design and finish Tesla is way behind BMW. They don't have the factories BMW does or any of the infrastructure and operational expertise. Tesla won't be able to compete in more the price sensitive "3" segment.
Perhaps Tesla would have been better if they only produced fast luxury cars. Too late for that now, though. The stock is priced based on promises of a mass adoption of the Model 3. A promise that they can't possibly deliver on. Unless Elon pulls another rabbit out of his hat. Wouldn't be the first time.