>In November 2018, SoftBank acquired a warrant to buy up to $3 billion worth of shares in the company by the end of September 2019 at a $42 billion valuation.
Valuation comes from how much stake you buy blown out as if the rest of the shares cost that much. This naturally doesn't make a lot of sense because the price would go up as you bought the rest of the shares. Still the valuation is ball park correct it was just a complete cock-up on the buyers part.
More SoftBank smoke and mirrors. Nobody was ever going to buy $3B at $42B valuation. Likely they were just doing that to give the appearance of such a valuation, aka, manipulating the public.