If you don't believe the Twitter stock is (going to be) worth anything why would you buy the stock? Of course a valuation is for the people who are optimistic

If you don't believe the Twitter stock is (going to be) worth anything why would you buy the stock? Of course a valuation is for the people who are optimistic about the future of the company, because that is who you are going to sell the stock to. A twenty fold increase in revenue is not at all unheard of, and as far as I know a standard estimate in the sector.