honest question: why would tesla, a responsible company, gamble so much money on a "product" which is literally worthless?
(is it because so much of their income is generated from selling credits?)
The same holds true for Bitcoin. The one (and only one) use case for Bitcoin is censorship resistant transactions. There will always be some subset of people that use Bitcoin as a legitimate way to transact; black market trading, drugs, people that live in countries that have unstable currencies, etc. This isn't a significant number of people, but it's non-zero. As long as there exists that set of people that legitimately use Bitcoin, Bitcoin has some intrinsic worth.