Existing investors can be onboard with the possibility of an exit even if it's less than their investment. From Fidelity's perspective they have a pile of money burned in a fire. Turning the ashes of that pile into what might be a swing for the fences or any type of exit at all is attractive. Also, sometimes good money follows bad to hedge against taking a larger loss on paper and in this case buying favor might get them access to another deal like SpaceX. None of it feels above board, an efficient market in action, or sane from most perspectives.