Tesla has much higher output than the number of vehicles that spontaneously combust. So the supply shortage you envision won’t occur unless cars light up by the hundreds or thousands a day. And that’s before accounting for all the extra slack in production created by decreasing demand around the world.

Teslas combusting damages the brand. It’s a material risk of owning a Tesla. It would also mean higher insurance. In fact beyond some combustion threshold, Teslas would become uninsurable. Therefore Teslas on fire directly contributes to decreasing Elon’s purchase power.