My immediate thoughts are... ...that I ought to invest, in advance, in a way that expects his ravings to cause a small panic, but then get myself positioned to ride back up the rebound too.
(I think that this is what Musk is doing/allowing to be done, based upon more immediate access to what whims and twists and turns he is prone to kick out there, seemingly at random. And if I have had the idea to try to 'pre-follow' the trends, I'm sure that people who are actually at the end of high-frequency-trading connections are already pre-second-guessing it all, which means of course that I'd be lucky to grab the scraps from the table of the complicated Futures markets within which all these gains (and losses!) are actually made into reality.)
Let the rich kids (really rich, rich on paper, rich in theory, rich in anticipation, whatever...) deal with it. I wouldn't consider any of this indicative of the On The Ground reality[1], just in the field where all the financial games are played.
Yes, the financial world can tear apart the 'real world' (various crashes leading to depressions, etc), but I'm not yet sure I'm willing to believe that one man can (intend to!) do this by a bit of Twittering, not without a whole lot of other supporting/opposing forces adding to the mess in their own way.
[1] Except insofar as his ability to start up, shut-down, expand, mothball, etc his own businesses. And possibly use his influence (or produce fall-out) to effect those other businesses supplying/being supplied by him.