The fact TSLA is valued more then all the auto manufactures combined is absurd. You're naive to think big auto is just going to sit on the sidelines. Big auto has the infrastructure and production lines to mass produce fully electric vehicles for a fraction of the cost of a TSLA, something TSLA will never be able do. Ford is already leading the charge with the F-150 Lightning and converting old factories into fully electric vehicle production plants. TSLA is just as overhyped as Elon Musk.
I do not think that there is this "big auto" that can stop him, or stop tesla because if there was one they would have already done that too long ago. However I think the appeal of Tesla is not about electric anymore, it is about brand, kind of like Steve Jobs made apple into because we all know that you could get a much better computer for the same price but people still do end up with mac, if it is about your work I could understand but people do it for show purposes and for the brand name as well.
Tesla is sort of like that, or becoming one at least, there are better cars out there for electric and much cheaper, there are cars one third of their price and it is still electric and it still goes, is it better? Probably not but hey it does the job and its very cheap, yet for some reason people still go for Tesla, why? Because, it is a symbol, it is basically a life style item if you can afford one.